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

vlib/sync/channel_polling_test.v

@@ -18,7 +18,7 @@ fn do_rec(ch chan int, resch chan i64, n int) {
 	mut sum := i64(0)
 	for _ in 0 .. n {
 		mut r := 0
-		for ch.try_pop(r) != .success {
+		for ch.try_pop(mut r) != .success {
 		}
 		sum += r
 	}

vlib/sync/channel_try_buf_test.v

@@ -7,7 +7,7 @@ fn test_channel_try_buffered() {
 		}
 	}
 	mut obj := int(0)
-	for ch.try_pop(obj) == .success {
+	for ch.try_pop(mut obj) == .success {
 		println(obj)
 	}
 	assert obj == 6

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
 }