Fix test_pkey_ec.rb on FIPS. #870

Job	Run time
openssl-1.0.2u	3m 7s
openssl-1.1.0l	2m 40s
openssl-1.1.1v	2m 56s
openssl-3.0.10	5m 29s
openssl-3.1.2	4m 21s
libressl-3.1.5	3m 37s
libressl-3.2.7	3m 8s
libressl-3.3.6	3m 49s
libressl-3.4.3	3m 13s
libressl-3.5.3	3m 14s
libressl-3.6.3	3m 15s
libressl-3.7.3	4m 0s
libressl-3.8.0	3m 13s
openssl-3.0.10 fips	4m 25s
openssl-3.1.2 fips	4m 34s
openssl-head	5m 30s
openssl-head fips	5m 14s
ruby-versions / Generate Ruby versions	5s
ubuntu-22.04 2.7	1m 25s
ubuntu-22.04 3.0	1m 15s
ubuntu-22.04 3.1	1m 28s
ubuntu-22.04 3.2	1m 12s
ubuntu-22.04 head	1m 11s
ubuntu-22.04 truffleruby	1m 45s
ubuntu-22.04 truffleruby-head	2m 41s
ubuntu-20.04 2.7	1m 27s
ubuntu-20.04 3.0	1m 8s
ubuntu-20.04 3.1	1m 8s
ubuntu-20.04 3.2	1m 19s
ubuntu-20.04 head	1m 16s
ubuntu-20.04 truffleruby-head	2m 9s
macos-latest 2.7	2m 21s
macos-latest 3.0	1m 20s
macos-latest 3.1	1m 23s
macos-latest 3.2	2m 9s
macos-latest head	1m 20s
macos-latest truffleruby-head	4m 34s
windows-latest 2.7	8m 13s
windows-latest 3.0	9m 53s
windows-latest 3.1	6m 29s
windows-latest 3.2	9m 0s
windows-latest ucrt	8m 4s
windows-latest mswin	4m 20s
	2h 24m 20s

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