build: fix pypa/gh-action-pypi-publish SHA

The previous SHA had a typo and didn't exist.

We will use the current stable SHA instead.

Author: dgw

.github/workflows/pypi.yml

@@ -22,6 +22,6 @@ jobs:
         run: |
           python -m build --sdist --wheel --outdir dist/ .
       - name: Publish distribution to PyPI
-        uses: pypa/gh-action-pypi-publish@2f6f737ca5f74c637829c0f5c3acd0e29ea5e8bf1
+        uses: pypa/gh-action-pypi-publish@81e9d935c883d0b210363ab89cf05f3894778450
         with:
           password: ${{ secrets.PYPI_TOKEN }}