🔇 Fix ruby 2.7 ivar not initialized warning

This looks like it was added for debugging, but it's unassigned and
unused now.  Future debuggers can easily add it back as needed.

test/net/imap/test_imap.rb

@@ -523,7 +523,7 @@ def tcp_socket(host, port)
           t: Process.clock_gettime(Process::CLOCK_MONOTONIC),
         }
         #super
-        s = Socket.tcp(host, port, :connect_timeout => @open_timeout)
+        s = Socket.tcp(host, port)
         @@h[:in_tcp_socket_2] = {
           s: s.inspect,
           local_address: s.local_address,