[DOC] Replace removed method in example for OpenSSL::Config#to_s #1186

Job	Run time
openssl-1.0.2u	2m 34s
openssl-1.1.0l	1m 36s
openssl-1.1.1w	1m 53s
openssl-3.0.15	3m 8s
openssl-3.1.7	3m 14s
openssl-3.2.3	3m 43s
openssl-3.3.2	3m 34s
openssl-master	3m 38s
libressl-3.1.5	2m 10s
libressl-3.2.7	2m 23s
libressl-3.3.6	2m 19s
libressl-3.4.3	2m 22s
libressl-3.5.3	2m 25s
libressl-3.6.3	2m 27s
libressl-3.7.3	2m 21s
libressl-3.8.4	2m 14s
libressl-3.9.2	2m 10s
openssl-3.0.15 with fips provider	2m 50s
openssl-3.1.7 with fips provider	2m 58s
openssl-3.2.3 with fips provider	3m 16s
openssl-3.3.2 with fips provider	3m 33s
openssl-master with fips provider	3m 25s
openssl-3.3.2 without legacy provider	3m 42s
ruby-versions / Generate Ruby versions	4s
ubuntu-22.04 2.7	59s
ubuntu-22.04 3.0	1m 1s
ubuntu-22.04 3.1	58s
ubuntu-22.04 3.2	1m 1s
ubuntu-22.04 3.3	1m 3s
ubuntu-22.04 head	57s
ubuntu-22.04 truffleruby	1m 36s
ubuntu-22.04 truffleruby-head	1m 48s
ubuntu-20.04 2.7	1m 1s
ubuntu-20.04 3.0	57s
ubuntu-20.04 3.1	54s
ubuntu-20.04 3.2	59s
ubuntu-20.04 3.3	1m 2s
ubuntu-20.04 head	57s
ubuntu-20.04 truffleruby	1m 34s
ubuntu-20.04 truffleruby-head	1m 51s
macos-latest 2.7	1m 1s
macos-latest 3.0	46s
macos-latest 3.1	56s
macos-latest 3.2	56s
macos-latest 3.3	47s
macos-latest head	42s
macos-latest truffleruby	1m 7s
macos-latest truffleruby-head	1m 22s
windows-latest 2.7	5m 44s
windows-latest 3.0	4m 7s
windows-latest 3.1	4m 11s
windows-latest 3.2	3m 46s
windows-latest 3.3	4m 52s
windows-latest head	3m 51s
windows-latest ucrt	3m 56s
windows-latest mswin	2m 57s
	2h 3m 38s

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