Fix a doc-nit in EVP_PKEY_CTX_ctrl.pod
[skip-ci] Reviewed-by:Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7546)
[skip-ci] Reviewed-by:Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7546)
mentioned in commit 0178459a
·mentioned in commit 0178459a