Fix test_pkey_rsa.rb in FIPS. #1155

Job	Run time
openssl-1.0.2u	53s
openssl-1.1.0l	59s
openssl-1.1.1w	59s
openssl-3.0.14	1m 1s
openssl-3.1.6	1m 9s
openssl-3.2.2	58s
openssl-3.3.1	1m 3s
openssl-master	3m 40s
libressl-3.1.5	55s
libressl-3.2.7	58s
libressl-3.3.6	59s
libressl-3.4.3	1m 0s
libressl-3.5.3	1m 5s
libressl-3.6.3	1m 6s
libressl-3.7.3	55s
libressl-3.8.4	1m 0s
libressl-3.9.2	1m 2s
openssl-3.0.14 with fips provider	44s
openssl-3.1.6 with fips provider	43s
openssl-3.2.2 with fips provider	37s
openssl-3.3.1 with fips provider	40s
openssl-master with fips provider	3m 17s
openssl-3.3.1 without legacy provider	1m 1s
ruby-versions / Generate Ruby versions	2s
ubuntu-22.04 2.7	1m 3s
ubuntu-22.04 3.0	56s
ubuntu-22.04 3.1	1m 3s
ubuntu-22.04 3.2	58s
ubuntu-22.04 3.3	59s
ubuntu-22.04 head	59s
ubuntu-22.04 truffleruby	1m 33s
ubuntu-22.04 truffleruby-head	1m 40s
ubuntu-20.04 2.7	57s
ubuntu-20.04 3.0	57s
ubuntu-20.04 3.1	58s
ubuntu-20.04 3.2	57s
ubuntu-20.04 3.3	54s
ubuntu-20.04 head	55s
ubuntu-20.04 truffleruby	1m 39s
ubuntu-20.04 truffleruby-head	1m 43s
macos-latest 2.7	54s
macos-latest 3.0	39s
macos-latest 3.1	43s
macos-latest 3.2	49s
macos-latest 3.3	40s
macos-latest head	47s
macos-latest truffleruby	1m 8s
macos-latest truffleruby-head	58s
windows-latest 2.7	6m 32s
windows-latest 3.0	4m 18s
windows-latest 3.1	3m 54s
windows-latest 3.2	3m 57s
windows-latest 3.3	4m 37s
windows-latest head	4m 1s
windows-latest ucrt	3m 42s
windows-latest mswin	2m 56s
	1h 25m 32s

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