fixup! test(ci): add changelog job that runs cargo xtask changelog

Author: ErichDonGubler

.github/workflows/changelog.yml

@@ -4,7 +4,6 @@ on:
   pull_request:
     paths:
       - 'CHANGELOG.md'
-  merge_group:
 
 env:
   #
@@ -36,8 +35,8 @@ jobs:
         uses: actions/checkout@v5
         with:
           fetch-depth: 0
-          ref: ${{ github.head_ref }}
+          ref: ${{ github.pull_request.head.ref }}
 
       - name: Run `cargo xtask changelog …`
         run: |
-          cargo xtask changelog "${{ github.base_ref }}"
+          cargo xtask changelog "${{ github.pull_request.base.ref }}"