make pub get test shufflable (#48095)

diff --git a/packages/flutter_tools/test/general.shard/dart/pub_get_test.dart b/packages/flutter_tools/test/general.shard/dart/pub_get_test.dart
index 99272c2..8b5eae7 100644
--- a/packages/flutter_tools/test/general.shard/dart/pub_get_test.dart
+++ b/packages/flutter_tools/test/general.shard/dart/pub_get_test.dart
@@ -31,6 +31,10 @@
     Cache.flutterRoot = getFlutterRoot();
   });
 
+  tearDown(() {
+    MockDirectory.findCache = false;
+  });
+
   testUsingContext('pub get 69', () async {
     String error;