Convert relative to absolute import. (flutter#135337)

Requested here: flutter#133952 (comment)

Author: polina-c

packages/flutter/lib/src/material/tab_controller.dart

@@ -4,9 +4,9 @@
 
 import 'dart:math' as math;
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
-import '../foundation/memory_allocations.dart';
 import 'constants.dart';
 
 // Examples can assume: