fix(tests): preventing test failure slipthrougs to main

The [checks for a PR](https://github.com/db-ux-design-system/core-web/actions/runs/17416146706/job/49445191771?pr=4904) run through smoothly, but it's results would lead to a [fail on `main` branch](https://github.com/db-ux-design-system/core-web/actions/runs/17421313490/job/49460006681). We need to prevent this to happen.

Author: mfranzke

.github/workflows/02-e2e-showcases.yml

@@ -77,7 +77,8 @@ jobs:
       # We test everything for patternhub and main branch
       - name: 👩‍🔬 Test showcase with Playwright 🎭
         shell: bash
-        if: github.event.pull_request == null
+        # TODO: we need to find a more stable solution
+        # if: github.event.pull_request == null
         env:
           NEXT_PUBLIC_BASE_PATH: ${{ inputs.path }}
         run: |