[element model] migrate _UninstantiatedBoundChecker

Change-Id: I3920bd9c22084a9bc5c29d5df28642362465da3b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/409440
Commit-Queue: Phil Quitslund <pquitslund@google.com>
Auto-Submit: Phil Quitslund <pquitslund@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/lib/src/generated/error_verifier.dart

@@ -6711,8 +6711,8 @@ class _UninstantiatedBoundChecker extends RecursiveAstVisitor<void> {
       return;
     }
 
-    var element = node.element;
-    if (element is TypeParameterizedElement && !element.isSimplyBounded) {
+    var element = node.element2;
+    if (element is TypeParameterizedElement2 && !element.isSimplyBounded) {
       // TODO(srawlins): Don't report this if TYPE_ALIAS_CANNOT_REFERENCE_ITSELF
       //  has been reported.
       _errorReporter.atNode(