GHA: use cPython 3.10.x versions as default

Author: chrissimpkins

.github/workflows/publish-release.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.9]
+        python-version: ["3.10"]
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python ${{ matrix.python-version }}

.github/workflows/py-lint.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: [3.9]
+        python-version: ["3.10"]
 
     steps:
       - uses: actions/checkout@v2

.github/workflows/py-typecheck.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: [3.9]
+        python-version: ["3.10"]
 
     steps:
       - uses: actions/checkout@v2