Replace deprecated kubebuilder action with recommended script

On-behalf-of: SAP <marvin.beckers@sap.com>
Signed-off-by: Marvin Beckers <marvin@kubermatic.com>

Author: embik

.github/workflows/pr-verifier.yaml

@@ -16,8 +16,28 @@ jobs:
       pull-requests: read
     runs-on: ubuntu-latest
     steps:
-    - name: Verifier action
-      id: verifier
-      uses: kubernetes-sigs/kubebuilder-release-tools@012269a88fa4c034a0acf1ba84c26b195c0dbab4 # tag=v0.4.3
-      with:
-        github_token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Checkout code
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # tag=v4.2.2
+
+      - name: Validate PR Title Format
+        run: |
+          TITLE="${{ github.event.pull_request.title }}"
+          
+          if [[ -z "$TITLE" ]]; then
+            echo "Error: PR title cannot be empty."
+            exit 1
+          fi
+          
+          if ! [[ "$TITLE" =~ ^($'\u26A0'|$'\u2728'|$'\U0001F41B'|$'\U0001F4D6'|$'\U0001F680'|$'\U0001F331') ]]; then
+            echo "Error: Invalid PR title format."
+            echo "Your PR title must start with one of the following indicators:"
+            echo "- Breaking change: ⚠ (U+26A0)"
+            echo "- Non-breaking feature: ✨ (U+2728)"
+            echo "- Patch fix: 🐛 (U+1F41B)"
+            echo "- Docs: 📖 (U+1F4D6)"
+            echo "- Release: 🚀 (U+1F680)"
+            echo "- Infra/Tests/Other: 🌱 (U+1F331)"
+            exit 1
+          fi
+          
+          echo "PR title is valid: '$TITLE'"