[GHA] Fix rebuild label (#5724)

actions/checkout v7 no longer allows checking out foreign repositories,
unless allow-unsafe-pr-checkout: true is specified.
This PR actually removes the foreign repo checkout, as the gh tool calls
should work on the base repo as well.

Signed-off-by: Holger Friedrich <mail@holger-friedrich.de>

.github/workflows/rebuild.yml

@@ -50,18 +50,11 @@ jobs:
         echo "$GITHUB"
 
     - name: Checkout
-      if: ${{ github.head_ref == '' && env.LABEL == 'rebuild' }}
+      if: ${{ env.LABEL == 'rebuild' }}
       uses: actions/checkout@v7
       with:
         persist-credentials: false
 
-    - name: Checkout merge
-      if: ${{ github.head_ref != '' && env.LABEL == 'rebuild' }}
-      uses: actions/checkout@v7
-      with:
-        ref: refs/pull/${{github.event.pull_request.number}}/merge
-        persist-credentials: false
-
     - name: List Jobs
       if: ${{ env.LABEL == 'rebuild' }}
       run: |