tidy_email_sendgrid is not compatible with cohttp 6

Fails with
```
=== ERROR while compiling tidy_email_sendgrid.0.0.1 ==========================#
 context              2.4.0~alpha1~dev | linux/x86_64 | ocaml-base-compiler.4.14.2 | file:///home/opam/opam-repository
 path                 ~/.opam/4.14/.opam-switch/build/tidy_email_sendgrid.0.0.1
 command              ~/.opam/opam-init/hooks/sandbox.sh build dune build -p tidy_email_sendgrid -j 39 @install
 exit-code            1
 env-file             ~/.opam/log/tidy_email_sendgrid-7-be480f.env
 output-file          ~/.opam/log/tidy_email_sendgrid-7-be480f.out
 (cd _build/default && /home/opam/.opam/4.14/bin/ocamlc.opt -w -40 -g -bin-annot -I sendgrid/src/.tidy_email_sendgrid.objs/byte -I /home/opam/.opam/4.14/lib/angstrom -I /home/opam/.opam/4.14/lib/astring -I /home/opam/.opam/4.14/lib/base64 -I /home/opam/.opam/4.14/lib/bigstringaf -I /home/opam/.opam/4.14/lib/bytes -I /home/opam/.opam/4.14/lib/cohttp -I /home/opam/.opam/4.14/lib/cohttp-lwt -I /home/opam/.opam/4.14/lib/cohttp-lwt-unix -I /home/opam/.opam/4.14/lib/conduit -I /home/opam/.opam/4.14/lib/conduit-lwt -I /home/opam/.opam/4.14/lib/conduit-lwt-unix -I /home/opam/.opam/4.14/lib/domain-name -I /home/opam/.opam/4.14/lib/fmt -I /home/opam/.opam/4.14/lib/http -I /home/opam/.opam/4.14/lib/ipaddr -I /home/opam/.opam/4.14/lib/ipaddr-sexp -I /home/opam/.opam/4.14/lib/ipaddr/unix -I /home/opam/.opam/4.14/lib/logs -I /home/opam/.opam/4.14/lib/lwt -I /home/opam/.opam/4.14/lib/lwt/unix -I /home/opam/.opam/4.14/lib/macaddr -I /home/opam/.opam/4.14/lib/magic-mime -I /home/opam/.opam/4.14/lib/ocaml/threads -I /home/opam/.opam/4.14/lib/ocplib-endian -I /home/opam/.opam/4.14/lib/ocplib-endian/bigstring -I /home/opam/.opam/4.14/lib/ppx_sexp_conv/runtime-lib -I /home/opam/.opam/4.14/lib/re -I /home/opam/.opam/4.14/lib/seq -I /home/opam/.opam/4.14/lib/sexplib0 -I /home/opam/.opam/4.14/lib/stringext -I /home/opam/.opam/4.14/lib/tidy_email -I /home/opam/.opam/4.14/lib/uri -I /home/opam/.opam/4.14/lib/uri-sexp -I /home/opam/.opam/4.14/lib/uri/services -I /home/opam/.opam/4.14/lib/yojson -intf-suffix .ml -no-alias-deps -o sendgrid/src/.tidy_email_sendgrid.objs/byte/tidy_email_sendgrid.cmo -c -impl sendgrid/src/tidy_email_sendgrid.pp.ml)
 File "sendgrid/src/tidy_email_sendgrid.ml", line 40, characters 16-47:
 40 |            ~ctx:Cohttp_lwt_unix.Net.default_ctx
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Error: This expression has type
          Cohttp_lwt_unix.Net.ctx Lazy.t = Cohttp_lwt_unix.Net.ctx lazy_t
        but an expression was expected of type
          Cohttp_lwt_unix.Client.ctx = Cohttp_lwt_unix.Net.ctx
 (cd _build/default && /home/opam/.opam/4.14/bin/ocamlopt.opt -w -40 -g -I sendgrid/src/.tidy_email_sendgrid.objs/byte -I sendgrid/src/.tidy_email_sendgrid.objs/native -I /home/opam/.opam/4.14/lib/angstrom -I /home/opam/.opam/4.14/lib/astring -I /home/opam/.opam/4.14/lib/base64 -I /home/opam/.opam/4.14/lib/bigstringaf -I /home/opam/.opam/4.14/lib/bytes -I /home/opam/.opam/4.14/lib/cohttp -I /home/opam/.opam/4.14/lib/cohttp-lwt -I /home/opam/.opam/4.14/lib/cohttp-lwt-unix -I /home/opam/.opam/4.14/lib/conduit -I /home/opam/.opam/4.14/lib/conduit-lwt -I /home/opam/.opam/4.14/lib/conduit-lwt-unix -I /home/opam/.opam/4.14/lib/domain-name -I /home/opam/.opam/4.14/lib/fmt -I /home/opam/.opam/4.14/lib/http -I /home/opam/.opam/4.14/lib/http/__private__/http_bytebuffer -I /home/opam/.opam/4.14/lib/ipaddr -I /home/opam/.opam/4.14/lib/ipaddr-sexp -I /home/opam/.opam/4.14/lib/ipaddr/unix -I /home/opam/.opam/4.14/lib/logs -I /home/opam/.opam/4.14/lib/lwt -I /home/opam/.opam/4.14/lib/lwt/unix -I /home/opam/.opam/4.14/lib/macaddr -I /home/opam/.opam/4.14/lib/magic-mime -I /home/opam/.opam/4.14/lib/ocaml/threads -I /home/opam/.opam/4.14/lib/ocplib-endian -I /home/opam/.opam/4.14/lib/ocplib-endian/bigstring -I /home/opam/.opam/4.14/lib/ppx_sexp_conv/runtime-lib -I /home/opam/.opam/4.14/lib/re -I /home/opam/.opam/4.14/lib/seq -I /home/opam/.opam/4.14/lib/sexplib0 -I /home/opam/.opam/4.14/lib/stringext -I /home/opam/.opam/4.14/lib/tidy_email -I /home/opam/.opam/4.14/lib/uri -I /home/opam/.opam/4.14/lib/uri-sexp -I /home/opam/.opam/4.14/lib/uri/services -I /home/opam/.opam/4.14/lib/yojson -intf-suffix .ml -no-alias-deps -o sendgrid/src/.tidy_email_sendgrid.objs/native/tidy_email_sendgrid.cmx -c -impl sendgrid/src/tidy_email_sendgrid.pp.ml)
 File "sendgrid/src/tidy_email_sendgrid.ml", line 40, characters 16-47:
 40 |            ~ctx:Cohttp_lwt_unix.Net.default_ctx
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Error: This expression has type
          Cohttp_lwt_unix.Net.ctx Lazy.t = Cohttp_lwt_unix.Net.ctx lazy_t
        but an expression was expected of type
          Cohttp_lwt_unix.Client.ctx = Cohttp_lwt_unix.Net.ctx
```

Signed-off-by: Marcello Seri <[email protected]>

packages/tidy_email_sendgrid/tidy_email_sendgrid.0.0.1/opam

@@ -13,7 +13,7 @@ depends: [
   "cmdliner" {>= "1.0.4" & with-test}
   "dune" {>= "2.8" & >= "2.0"}
   "ocaml" {>= "4.11.0"}
-  "cohttp" {>= "2.5.5"}
+  "cohttp" {>= "2.5.5" & < "6.0~~"}
   "cohttp-lwt-unix" {>= "2.5.5"}
   "lwt_ppx" {>= "2.0.0"}
   "yojson" {>= "1.7.0"}