Fix test_pkey_rsa.rb in FIPS. #1156

Job	Run time
openssl-1.0.2u	56s
openssl-1.1.0l	50s
openssl-1.1.1w	54s
openssl-3.0.14	1m 2s
openssl-3.1.6	57s
openssl-3.2.2	57s
openssl-3.3.1	1m 0s
openssl-master	3m 36s
libressl-3.1.5	53s
libressl-3.2.7	1m 4s
libressl-3.3.6	1m 7s
libressl-3.4.3	1m 0s
libressl-3.5.3	1m 3s
libressl-3.6.3	59s
libressl-3.7.3	1m 3s
libressl-3.8.4	1m 4s
libressl-3.9.2	57s
openssl-3.0.14 with fips provider	44s
openssl-3.1.6 with fips provider	45s
openssl-3.2.2 with fips provider	40s
openssl-3.3.1 with fips provider	39s
openssl-master with fips provider	3m 19s
openssl-3.3.1 without legacy provider	1m 9s
ruby-versions / Generate Ruby versions	2s
ubuntu-22.04 2.7	1m 2s
ubuntu-22.04 3.0	58s
ubuntu-22.04 3.1	1m 4s
ubuntu-22.04 3.2	1m 0s
ubuntu-22.04 3.3	1m 3s
ubuntu-22.04 head	1m 7s
ubuntu-22.04 truffleruby	1m 35s
ubuntu-22.04 truffleruby-head	1m 42s
ubuntu-20.04 2.7	1m 0s
ubuntu-20.04 3.0	54s
ubuntu-20.04 3.1	57s
ubuntu-20.04 3.2	1m 1s
ubuntu-20.04 3.3	56s
ubuntu-20.04 head	55s
ubuntu-20.04 truffleruby	1m 31s
ubuntu-20.04 truffleruby-head	1m 37s
macos-latest 2.7	1m 0s
macos-latest 3.0	44s
macos-latest 3.1	48s
macos-latest 3.2	43s
macos-latest 3.3	50s
macos-latest head	45s
macos-latest truffleruby	1m 2s
macos-latest truffleruby-head	1m 28s
windows-latest 2.7	4m 55s
windows-latest 3.0	3m 57s
windows-latest 3.1	4m 24s
windows-latest 3.2	4m 5s
windows-latest 3.3	4m 51s
windows-latest head	3m 50s
windows-latest ucrt	3m 46s
windows-latest mswin	2m 54s
	1h 25m 4s

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