Pass through nil as digest when signing certificates #1076

Job	Run time
openssl-1.0.2u	2m 25s
openssl-1.1.0l	1m 33s
openssl-1.1.1w	1m 39s
openssl-3.0.13	2m 47s
openssl-3.1.5	2m 51s
openssl-3.2.1	3m 21s
openssl-3.3.0	3m 21s
libressl-3.1.5	2m 6s
libressl-3.2.7	2m 37s
libressl-3.3.6	2m 13s
libressl-3.4.3	2m 25s
libressl-3.5.3	2m 26s
libressl-3.6.3	2m 15s
libressl-3.7.3	2m 15s
libressl-3.8.4	2m 14s
libressl-3.9.1	2m 20s
openssl-3.0.13 fips	2m 47s
openssl-3.1.5 fips	2m 59s
openssl-3.2.1 fips	3m 12s
openssl-3.3.0 fips	3m 17s
openssl-head	3m 59s
openssl-head fips	3m 27s
openssl-head no-legacy	3m 33s
ruby-versions / Generate Ruby versions	7s
ubuntu-22.04 2.7	57s
ubuntu-22.04 3.0	54s
ubuntu-22.04 3.1	1m 5s
ubuntu-22.04 3.2	1m 0s
ubuntu-22.04 3.3	59s
ubuntu-22.04 head	1m 1s
ubuntu-22.04 truffleruby	1m 37s
ubuntu-22.04 truffleruby-head	1m 45s
ubuntu-20.04 2.7	57s
ubuntu-20.04 3.0	56s
ubuntu-20.04 3.1	55s
ubuntu-20.04 3.2	55s
ubuntu-20.04 3.3	58s
ubuntu-20.04 head	54s
ubuntu-20.04 truffleruby-head	1m 43s
macos-latest 2.7	49s
macos-latest 3.0	44s
macos-latest 3.1	46s
macos-latest 3.2	39s
macos-latest 3.3	41s
macos-latest head	40s
macos-latest truffleruby-head	1m 4s
windows-latest 2.7	5m 52s
windows-latest 3.0	4m 19s
windows-latest 3.1	4m 15s
windows-latest 3.2	5m 19s
windows-latest 3.3	5m 27s
windows-latest head	4m 17s
windows-latest ucrt	3m 35s
windows-latest mswin	2m 31s
	1h 59m 43s

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