ubuntu-18.04->20.04

.github/workflows/docs-release.yml

@@ -8,7 +8,7 @@ on:
 jobs:
   API_Document_Release:
     name: API Document Release
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
     - name: Syncing the webhook
       env:

.github/workflows/publish-to-test-pypi.yml

@@ -3,7 +3,7 @@ on: push
 jobs:
   build-n-publish:
     name: Build and publish Python distributions to PyPI
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@master
       - name: Set up Python 3.8

.github/workflows/py.yml

@@ -12,7 +12,7 @@ on:
 jobs:
   check_license_and_format:
     name: License and format
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     if: github.event.pull_request.draft == false && contains(github.event.pull_request.requested_reviewers.*.login, 'oneflow-ci-bot')
     steps:
       - uses: actions/checkout@v2