Fix obsolete `CronetClient()` constructor usage #853

Job	Run time
mono_repo self validate	17s
analyze_and_format; Dart 2.19.0; PKG: pkgs/http_client_conformance_tests; `dart analyze --fatal-i...	28s
analyze_and_format; Dart 3.0.0; PKGS: pkgs/http, pkgs/http_profile; `dart analyze --fatal-infos`	27s
analyze_and_format; Dart dev; PKGS: pkgs/http, pkgs/http_client_conformance_tests, pkgs/http_prof...	37s
analyze_and_format; Dart dev; PKGS: pkgs/http, pkgs/http_client_conformance_tests, pkgs/http_prof...	19s
unit_test; Dart 3.0.0; PKG: pkgs/http; `dart run --define=no_default_http_client=true test/no_def...	24s
unit_test; Dart 3.0.0; PKGS: pkgs/http, pkgs/http_profile; `dart test --platform vm`	1m 12s
unit_test; Dart 3.0.0; PKG: pkgs/http; `dart test --platform chrome`	3m 29s
unit_test; Dart dev; PKG: pkgs/http; `dart test --platform chrome`	1m 21s
unit_test; Dart dev; PKG: pkgs/http; `dart run --define=no_default_http_client=true test/no_defau...	33s
unit_test; Dart dev; PKGS: pkgs/http, pkgs/http_profile; `dart test --platform vm`	45s
	9m 52s

Provide feedback