Bug 1757407 - Allow a third duplicated instance of tokio; r=firefox-build-system-reviewers,glandium

Unfortunately, the dependencies of l10nregistry-rs require tokio 1.0. This
allows this third duplicated instance. I think it makes more sense to try to
move the other uses in tree to a more modern version than to try to downgrade
the version of tokio required by l10nregistry-rs and dependencies.

Differential Revision: https://phabricator.services.mozilla.com/D139854

python/mozbuild/mozbuild/vendor/vendor_rust.py

@@ -89,7 +89,7 @@ TOLERATED_DUPES = {
     "mio": 2,
     "pin-project-lite": 2,
     "target-lexicon": 2,
-    "tokio": 2,
+    "tokio": 3,
 }