Temporarily don't fail on EPUB check fatal errors

Author: m-aciek

.github/workflows/reusable-docs.yml

@@ -84,6 +84,7 @@ jobs:
         epubcheck Doc/build/epub/Python.epub &> Doc/epubcheck.txt
     - name: 'Check for fatal errors in EPUB'
       if: github.event_name == 'pull_request'
+      continue-on-error: true  # temporarily, until gh-136155 is fixed
       run: |
         python Doc/tools/check-epub.py