Tests: relaxed mail_imap_ssl.t cipher matching. Previously, exact match between cipher name in the log and the one from IO::Socket:SSL was needed, which might not be the case if nginx and Net::SSLeay are compiled with different SSL libraries, notably LibreSSL (which uses names like AEAD-AES256-GCM-SHA384 till 3.5.0), and OpenSSL or BoringSSL (which use TLS_AES_256_GCM_SHA384). In particular, this affects macOS, where Net::SSLeay compiled with LibreSSL 3.3.6 is shipped with the OS, while nginx is likely to be compiled with OpenSSL. Fix is to not require exact match but instead accept properly looking names as checked by a regular expression, similarly to how it is already tested in ssl.t and stream_ssl_variables.t.