Update Python used in publish.yml to 3.9

Author: tkf

.github/workflows/publish.yml

@@ -13,10 +13,10 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
-      - name: Set up Python 3.8
+      - name: Set up Python 3.9
         uses: actions/setup-python@v1
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Install setuptools and wheel
         run: |
           python -m pip install --user setuptools wheel
@@ -40,10 +40,10 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
-      - name: Set up Python 3.8
+      - name: Set up Python 3.9
         uses: actions/setup-python@v1
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Set up Julia
         uses: julia-actions/setup-julia@v1
         with:
@@ -59,10 +59,10 @@ jobs:
       matrix:  # using `matrix` to define a constant
         package: ['julia==0.5.7.dev']
     steps:
-      - name: Set up Python 3.8
+      - name: Set up Python 3.9
         uses: actions/setup-python@v1
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Download from TestPyPI
         run: |
           pip download --dest dist --no-deps --index-url https://test.pypi.org/simple/ ${{ matrix.package }}