parser: enable module auto import (of sync) (#6271)

vlib/sync/channel_2_test.v

@@ -1,23 +1,19 @@
-import sync
-
 const (
 	num_iterations = 10000
 )
 
-fn do_send(mut ch sync.Channel) {
+fn do_send(ch chan int) {
 	for i in 0 .. num_iterations {
-		ch.push(&i)
+		ch <- i
 	}
 }
 
 fn test_channel_unbuffered() {
-	mut ch := sync.new_channel<int>(0)
-	go do_send(mut ch)
+	ch := chan int{}
+	go do_send(ch)
 	mut sum := i64(0)
 	for _ in 0 .. num_iterations {
-		a := 0
-		ch.pop(&a)
-		sum += a
+		sum += <-ch
 	}
 	assert sum == u64(num_iterations)*(num_iterations-1)/2
 }