Add test for assert!() hygiene in edition 2021.

Author: m-ou-se

src/test/ui/hygiene/no_implicit_prelude-2021.rs

@@ -0,0 +1,9 @@
+// check-pass
+// edition:2021
+
+#![no_implicit_prelude]
+
+fn main() {
+    assert!(true, "hoi");
+    assert!(false, "hoi {}", 123);
+}