[INTPROD-1125] Update Runner for GH Action

Author: colinsl

.github/workflows/pull_request.yml

@@ -1,7 +1,7 @@
 on: pull_request
 jobs:
   pre-commit:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v1
@@ -14,7 +14,7 @@ jobs:
       - name: Run pre-commit
         run: pre-commit run --all-files
   test:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         python-version: ['2.x', '3.x']