Update pub to use the VM's new bad-snapshot exit code.

sdk/lib/_internal/pub_generated/test/global/activate/outdated_binstub_test.dart

Index: sdk/lib/_internal/pub_generated/test/global/activate/outdated_binstub_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/global/activate/outdated_binstub_test.dart b/sdk/lib/_internal/pub_generated/test/global/activate/outdated_binstub_test.dart
index 65fd10b80a1d0eee4fde066fdb86b5e4f806b199..74d5408dd2127f6ca166fdd4ebedf7463cf2bf59 100644
--- a/sdk/lib/_internal/pub_generated/test/global/activate/outdated_binstub_test.dart
+++ b/sdk/lib/_internal/pub_generated/test/global/activate/outdated_binstub_test.dart
@@ -47,9 +47,9 @@ main() {
 
     d.dir(
         cachePath,
-        [d.dir('bin', [// 255 is the VM's exit code upon seeing an out-of-date snapshot.
+        [d.dir('bin', [// 253 is the VM's exit code upon seeing an out-of-date snapshot.
         d.matcherFile(
             binStubName('foo-script'),
-            contains("255"))])]).validate();
+            contains("253"))])]).validate();
   });
 }