Fix overzealous rename.

In 79974bb02605d0cc16c8a8bda8de23920a890649 I accidentally renamed one
of the withNullability methods, causing it to become disconnected from
the method it was overriding.  This CL undoes the bogus rename.

Change-Id: I24655d76ef5c602e967a055e86d072a87435f3a5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/99480
Commit-Queue: Paul Berry <paulberry@google.com>
Commit-Queue: Dan Rubel <danrubel@google.com>
Auto-Submit: Paul Berry <paulberry@google.com>
Reviewed-by: Dan Rubel <danrubel@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
diff --git a/pkg/analyzer/lib/src/dart/element/type.dart b/pkg/analyzer/lib/src/dart/element/type.dart
index 60b2d25..f3a5c7f 100644
--- a/pkg/analyzer/lib/src/dart/element/type.dart
+++ b/pkg/analyzer/lib/src/dart/element/type.dart
@@ -237,7 +237,7 @@
   FunctionTypeImpl substitute3(List<DartType> argumentTypes) => this;
 
   @override
-  TypeImpl withNullabilitySuffix(NullabilitySuffix nullabilitySuffix) => this;
+  TypeImpl withNullability(NullabilitySuffix nullabilitySuffix) => this;
 
   @override
   void _forEachParameterType(