Build with Ubuntu 20.04 to be more compatible with Google Colab (#511)

.github/workflows/python-package.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        os: [ubuntu-20.04, macos-latest, windows-latest]
         python-version: ["3.8", "3.9", "3.10", "3.11"]
 
     steps:

.github/workflows/python-publish.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        os: [ubuntu-20.04, macos-latest, windows-latest]
         python-version: ["3.8", "3.9", "3.10", "3.11"]
         
     steps:
@@ -46,7 +46,7 @@ jobs:
       run: python setup.py bdist_wheel
         
     - name: Rename Linux wheels to supported platform of PyPI
-      if: matrix.os == 'ubuntu-latest'
+      if: matrix.os == 'ubuntu-20.04'
       run: for f in dist/*.whl; do mv "$f" "$(echo "$f" | sed s/linux/manylinux1/)"; done
 
     - name: Publish wheels to GitHub artifacts
@@ -58,7 +58,7 @@ jobs:
 
   publish-pypi:
     needs: [build-wheels]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2