sync_typeshed: add fetch-depth: 0 (#13899)

Otherwise the commit it wants to cherry-pick doesn't exist:
https://github.com/python/mypy/actions/runs/3253702865/jobs/5341201852

Author: JelleZijlstra

.github/workflows/sync_typeshed.yml

@@ -16,6 +16,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
         # TODO: use whatever solution ends up working for
         # https://github.com/python/typeshed/issues/8434
       - uses: actions/setup-python@v4