Fix crd-size-badge checkout for pull_request_target

actions/checkout v7 now blocks fork PR checkout in pull_request_target
workflows by default. This workflow only measures CRD file size and
posts a comment, so allow-unsafe-pr-checkout is safe here.

Author: stuggi

.github/workflows/crd-size-badge.yaml

@@ -21,6 +21,7 @@ jobs:
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
         with:
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
+          allow-unsafe-pr-checkout: true
 
       - name: Install yq
         uses: mikefarah/yq@1b9b4ac5187171d2e5e3129be0cfa827c7f9d53d # v4