check-changeset was missing fetch-depth

Author: hsubox76

.github/workflows/check-changeset.yml

@@ -12,6 +12,7 @@ jobs:
       uses: actions/checkout@master
       with:
         # This makes Actions fetch all Git history so check_changeset script can diff properly.
+        fetch-depth: 0
     - name: Set up Node (10)
       uses: actions/setup-node@v1
       with: