ci: make the PR size check advisory (non-blocking)

Author: dannywillems

.github/workflows/pr-hygiene.yaml

@@ -14,6 +14,8 @@ jobs:
   check-pr-size:
     name: Check PR size
     runs-on: ubuntu-latest
+    # Advisory only: report the size but never block the PR.
+    continue-on-error: true
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with: