[Coroutines] Make suspend_always in test noexcept (NFC)

Author: ChuanqiXu9

clang/test/CodeGenCoroutines/Inputs/coroutine.h

@@ -67,9 +67,9 @@ template <typename Promise> struct coroutine_handle : coroutine_handle<> {
   }
 
 struct suspend_always {
-  bool await_ready() { return false; }
-  void await_suspend(coroutine_handle<>) {}
-  void await_resume() {}
+  bool await_ready() noexcept { return false; }
+  void await_suspend(coroutine_handle<>) noexcept {}
+  void await_resume() noexcept {}
 };
 struct suspend_never {
   bool await_ready() noexcept { return true; }