Auto merge of #22961 - servo:jdm-patch-19, r=jdm

Force a pickling protocol that will accept certain awkward classes.

This cherry-picks the important part of https://github.com/web-platform-tests/wpt/pull/15611 to unbreak the nightly WPT sync.

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tests/wpt/metadata/MANIFEST.json

@@ -683466,7 +683466,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/update/state.py": [
-   "dc459da7e2e5a6b5dfd088b711e4fa9c7d693af9",
+   "3a97618effdbf13c22ac422a6f5e4bbae65643bd",
    "support"
   ],
   "tools/wptrunner/wptrunner/update/sync.py": [

tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/update/state.py

@@ -69,7 +69,7 @@ class State(object):
     def save(self):
         """Write the state to disk"""
         with open(self.filename, "w") as f:
-            pickle.dump(self, f)
+            pickle.dump(self, f, 2)
 
     def is_empty(self):
         return len(self._data) == 1 and self._data[0] == {}