💥 Do not mixin OpenSSL::SSL module

`Net::IMAP` has mixed in `OpenSSL::SSL` since it first added TLS
support.  But that isn't very helpful, and it clutters up the namespace
with irrelevant constants.

I doubt anyone is actually _using_ OpenSSL constants from Net::IMAP.  I
hope not.  Nevertheless, this is a breaking change.

Author: nevans

lib/net/imap.rb

@@ -804,10 +804,6 @@ class IMAP < Protocol
     autoload :StringPrep,             "#{dir}/stringprep"
 
     include MonitorMixin
-    if defined?(OpenSSL::SSL)
-      include OpenSSL
-      include SSL
-    end
 
     # Returns the global Config object
     def self.config; Config.global end