Fix pypi workflow (increae ubuntu version)

Author: cokelaer

.github/workflows/pypi.yml

@@ -8,9 +8,9 @@ on:
 jobs:
   build-n-publish:
     name: Build and publish to PyPI and TestPyPI
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@main
     - name: Set up Python 3.7
       uses: actions/setup-python@v1
       with:
@@ -26,14 +26,14 @@ jobs:
           python setup.py sdist
 
     - name: Publish distribution to Test PyPI
-      uses: pypa/gh-action-pypi-publish@master
+      uses: pypa/gh-action-pypi-publish@release/v1
       with:
         user: __token__
         password: ${{ secrets.TEST_PYPI_API_TOKEN }}
         repository_url: https://test.pypi.org/legacy/
     - name: Publish distribution to PyPI
       if: startsWith(github.ref, 'refs/tags')
-      uses: pypa/gh-action-pypi-publish@master
+      uses: pypa/gh-action-pypi-publish@release/v1
       with:
         user: __token__
         password: ${{ secrets.PYPI_API_TOKEN }}