checker: check argument for chan.try_push/pop() (#9798)

vlib/sync/channel_try_unbuf_test.v

@@ -8,6 +8,6 @@ fn test_channel_try_unbuffered() {
 		panic('push on non-ready channel not detected')
 	}
 	mut obj := -17
-	for ch.try_pop(obj) == .success {}
+	for ch.try_pop(mut obj) == .success {}
 	assert obj == -17
 }