chore(deps): update actions/checkout action to v2 (#139)

Co-authored-by: Maggie Nolan <nolanmar@google.com>

Author: renovate-bot

.github/workflows/ci.yaml

@@ -11,7 +11,7 @@ jobs:
       matrix:
         node: [ 10, 12, 14]
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - uses: actions/setup-node@v1
         with:
           node-version: ${{ matrix.node }}
@@ -38,7 +38,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - uses: actions/setup-node@v1
         with:
           node-version: 14