Report wrong async function result type as type error in checked mode (Fixes #26133).

runtime/vm/ast.h

Index: runtime/vm/ast.h
diff --git a/runtime/vm/ast.h b/runtime/vm/ast.h
index 13184af4143c856db692ed5db510c96732da660c..790e94ccfb7bacfa7eb809b692d0be3392f8446f 100644
--- a/runtime/vm/ast.h
+++ b/runtime/vm/ast.h
@@ -616,7 +616,7 @@ class PrimaryNode : public AstNode {
   DISALLOW_IMPLICIT_CONSTRUCTORS(PrimaryNode);
 };
 
-// In asynchronous code that gets suspeded and resumed, return nodes
+// In asynchronous code that gets suspended and resumed, return nodes
 // can be of different types:
 // * A regular return node that in the case of async functions
 //    gets replaced with appropriate completer calls. (kRegular)