Fix test_pkey_ec.rb on FIPS. #866

Job	Run time
openssl-1.0.2u	3m 36s
openssl-1.1.0l	2m 5s
openssl-1.1.1v	2m 26s
openssl-3.0.10	4m 29s
openssl-3.1.2	4m 28s
libressl-3.1.5	3m 8s
libressl-3.2.7	4m 2s
libressl-3.3.6	4m 9s
libressl-3.4.3	4m 6s
libressl-3.5.3	3m 45s
libressl-3.6.3	3m 5s
libressl-3.7.3	3m 37s
libressl-3.8.0	3m 30s
openssl-3.0.10 fips	4m 20s
openssl-3.1.2 fips	4m 25s
openssl-head	7m 20s
openssl-head fips	5m 8s
ruby-versions / Generate Ruby versions	2s
ubuntu-22.04 2.7	1m 22s
ubuntu-22.04 3.0	1m 6s
ubuntu-22.04 3.1	1m 15s
ubuntu-22.04 3.2	1m 31s
ubuntu-22.04 head	1m 10s
ubuntu-22.04 truffleruby	1m 37s
ubuntu-22.04 truffleruby-head	1m 55s
ubuntu-20.04 2.7	1m 28s
ubuntu-20.04 3.0	1m 22s
ubuntu-20.04 3.1	1m 7s
ubuntu-20.04 3.2	1m 31s
ubuntu-20.04 head	1m 6s
ubuntu-20.04 truffleruby-head	1m 52s
macos-latest 2.7	2m 1s
macos-latest 3.0	1m 57s
macos-latest 3.1	1m 41s
macos-latest 3.2	1m 41s
macos-latest head	1m 27s
macos-latest truffleruby-head	4m 17s
windows-latest 2.7	6m 29s
windows-latest 3.0	7m 33s
windows-latest 3.1	6m 16s
windows-latest 3.2	7m 20s
windows-latest ucrt	6m 14s
windows-latest mswin	5m 12s
	2h 18m 11s

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