[ruby/openssl] Fix OCSP documentation

`port` should be called on the `ocsp_uri` URI instead of `ocsp`, which
is just a string.

https://github.com/ruby/openssl/commit/89a1c82dd0

ext/openssl/ossl_ocsp.c

@@ -1701,7 +1701,7 @@ Init_ossl_ocsp(void)
      *   require 'net/http'
      *
      *   http_response =
-     *     Net::HTTP.start ocsp_uri.hostname, ocsp.port do |http|
+     *     Net::HTTP.start ocsp_uri.hostname, ocsp_uri.port do |http|
      *       http.post ocsp_uri.path, request.to_der,
      *                 'content-type' => 'application/ocsp-request'
      *   end