[CI] merge all ci tests into one file (#1289)

.github/workflows/lint.yml

@@ -1,19 +1,22 @@
 name: Lint
 
-on: [push, pull_request]
+on: [pull_request]
 
 jobs:
   lint:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - name: Set up Python 3.8
+
+      - name: Set up Python 3.9
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.9
+
       - name: Install pre-commit hook
         run: |
           python -m pip install pre-commit
           pre-commit install
+
       - name: Linting
         run: pre-commit run --all-files