Fix actions/upload-pages-artifact version comment

Signed-off-by: James Taylor <jamest@uk.ibm.com>

Author: jt-nti

.github/workflows/mkdocs.yml

@@ -44,7 +44,7 @@ jobs:
       - name: Build with mkdocs
         run: mkdocs build --strict
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@7b1f4a764d45c48632c6b24a0339c27f5614fb0b # v3
+        uses: actions/upload-pages-artifact@7b1f4a764d45c48632c6b24a0339c27f5614fb0b # v4.0.0
         with:
           path: ./site