Bug 1805263 - [ci] Revert 'release-flatpack-repackage' tasks back to AWS, r=releng-reviewers,aki

We had https://bugzilla.mozilla.org/show_bug.cgi?id=1795884 on file for this already, but the
task passes on try and I must have unwittingly re-landed it again.

Differential Revision: https://phabricator.services.mozilla.com/D164482

taskcluster/ci/release-flatpak-repackage/kind.yml

@@ -24,7 +24,7 @@ job-defaults:
         platform: linux64-shippable/opt
         kind: build
         tier: 2
-    worker-type: b-linux-gcp
+    worker-type: b-linux
     worker:
         implementation: docker-worker
         os: linux