Add missing logger spec for cowboy_http2 opts

src/cowboy_http2.erl

@@ -33,6 +33,7 @@
 	inactivity_timeout => timeout(),
 	initial_connection_window_size => 65535..16#7fffffff,
 	initial_stream_window_size => 0..16#7fffffff,
+	logger => module(),
 	max_concurrent_streams => non_neg_integer() | infinity,
 	max_decode_table_size => non_neg_integer(),
 	max_encode_table_size => non_neg_integer(),