Fix test_pkey_ec.rb on FIPS. #865

Job	Run time
openssl-1.0.2u	3m 41s
openssl-1.1.0l	3m 13s
openssl-1.1.1v	2m 24s
openssl-3.0.10	5m 20s
openssl-3.1.2	4m 17s
libressl-3.1.5	3m 3s
libressl-3.2.7	3m 46s
libressl-3.3.6	3m 13s
libressl-3.4.3	3m 43s
libressl-3.5.3	3m 44s
libressl-3.6.3	3m 7s
libressl-3.7.3	3m 23s
libressl-3.8.0	3m 15s
openssl-3.0.10 fips	5m 33s
openssl-3.1.2 fips	4m 18s
openssl-head	5m 27s
openssl-head fips	6m 22s
ruby-versions / Generate Ruby versions	4s
ubuntu-22.04 2.7	1m 23s
ubuntu-22.04 3.0	1m 5s
ubuntu-22.04 3.1	1m 16s
ubuntu-22.04 3.2	1m 35s
ubuntu-22.04 head	1m 20s
ubuntu-22.04 truffleruby	1m 37s
ubuntu-22.04 truffleruby-head	2m 36s
ubuntu-20.04 2.7	1m 10s
ubuntu-20.04 3.0	1m 20s
ubuntu-20.04 3.1	1m 7s
ubuntu-20.04 3.2	1m 22s
ubuntu-20.04 head	1m 3s
ubuntu-20.04 truffleruby-head	2m 24s
macos-latest 2.7	1m 51s
macos-latest 3.0	1m 41s
macos-latest 3.1	1m 24s
macos-latest 3.2	1m 27s
macos-latest head	1m 41s
macos-latest truffleruby-head	3m 40s
windows-latest 2.7	5m 17s
windows-latest 3.0	8m 12s
windows-latest 3.1	6m 4s
windows-latest 3.2	7m 40s
windows-latest ucrt	6m 48s
windows-latest mswin	5m 7s
	2h 18m 3s

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