Fix test_pkey_rsa.rb in FIPS. #1159

Job	Run time
openssl-1.0.2u	51s
openssl-1.1.0l	54s
openssl-1.1.1w	1m 16s
openssl-3.0.14	1m 2s
openssl-3.1.6	58s
openssl-3.2.2	1m 1s
openssl-3.3.1	58s
openssl-master	4m 16s
libressl-3.1.5	54s
libressl-3.2.7	59s
libressl-3.3.6	1m 4s
libressl-3.4.3	1m 10s
libressl-3.5.3	1m 6s
libressl-3.6.3	1m 5s
libressl-3.7.3	1m 5s
libressl-3.8.4	1m 6s
libressl-3.9.2	1m 6s
openssl-3.0.14 with fips provider	41s
openssl-3.1.6 with fips provider	47s
openssl-3.2.2 with fips provider	38s
openssl-3.3.1 with fips provider	48s
openssl-master with fips provider	3m 41s
openssl-3.3.1 without legacy provider	56s
ruby-versions / Generate Ruby versions	6s
ubuntu-22.04 2.7	1m 3s
ubuntu-22.04 3.0	58s
ubuntu-22.04 3.1	1m 4s
ubuntu-22.04 3.2	1m 17s
ubuntu-22.04 3.3	1m 2s
ubuntu-22.04 head	1m 5s
ubuntu-22.04 truffleruby	1m 43s
ubuntu-22.04 truffleruby-head	1m 54s
ubuntu-20.04 2.7	1m 2s
ubuntu-20.04 3.0	56s
ubuntu-20.04 3.1	56s
ubuntu-20.04 3.2	1m 7s
ubuntu-20.04 3.3	1m 10s
ubuntu-20.04 head	57s
ubuntu-20.04 truffleruby	1m 39s
ubuntu-20.04 truffleruby-head	1m 41s
macos-latest 2.7	1m 17s
macos-latest 3.0	42s
macos-latest 3.1	44s
macos-latest 3.2	1m 7s
macos-latest 3.3	49s
macos-latest head	50s
macos-latest truffleruby	1m 11s
macos-latest truffleruby-head	1m 34s
windows-latest 2.7	5m 9s
windows-latest 3.0	4m 26s
windows-latest 3.1	4m 1s
windows-latest 3.2	5m 36s
windows-latest 3.3	6m 9s
windows-latest head	4m 17s
windows-latest ucrt	4m 3s
windows-latest mswin	3m 0s
	1h 32m 57s

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