Fix action version (#111)

Apparently dependabot failed to propose new versions for this likely because original tag did not exist.

.github/workflows/release.yml

@@ -43,6 +43,6 @@ jobs:
     - name: Publish to pypi.org
       if: >-  # "create" workflows run separately from "push" & "pull_request"
         github.event_name == 'release'
-      uses: pypa/gh-action-pypi-publish@v1
+      uses: pypa/gh-action-pypi-publish@v1.5.1
       with:
         password: ${{ secrets.pypi_password }}