Remove superfluous flag in SPHINXOPTS, shorten step name

Author: m-aciek

.github/workflows/reusable-docs.yml

@@ -104,7 +104,7 @@ jobs:
       run: xvfb-run make -C Doc/ PYTHON=../python SPHINXERRORHANDLING="--fail-on-warning" doctest
 
   epubcheck:
-    name: 'Docs EPUB check'
+    name: 'EPUB check'
     runs-on: ubuntu-latest
     timeout-minutes: 40
     steps:
@@ -130,7 +130,7 @@ jobs:
       continue-on-error: true
       run: |
         set -Eeuo pipefail
-        make -C Doc/ PYTHON=../python SPHINXOPTS="--quiet --fail-on-warning" epub
+        make -C Doc/ PYTHON=../python SPHINXOPTS="--quiet" epub
         pip install epubcheck
         epubcheck Doc/build/epub/Python.epub &> Doc/epubcheck.txt
     - name: 'Check for FATAL errors in EPUB'