ci: fix check syntax for branch name

Author: sgratzl

.github/workflows/ci.yaml

@@ -87,7 +87,7 @@ jobs:
   image:
     needs: build
     # only on main and dev branch
-    if: startsWith(github.ref, 'refs/heads/main') || github.ref == 'refs/heads/dev'
+    if: github.ref == 'refs/heads/main' || github.ref == 'refs/heads/dev'
     runs-on: ubuntu-latest
     steps:
       - name: Check out code