build: release job needs full checkout with tags

.github/workflows/build-syncthing.yaml

@@ -782,6 +782,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          ref: ${{ github.ref }} # https://github.com/actions/checkout/issues/882
 
       - name: Download signed packages
         uses: actions/download-artifact@v4