chore(deps): bump actions/checkout from v1 to v2.3.4

Bumps [actions/checkout](https://github.com/actions/checkout) from v1 to v2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v1...5a4ac90)

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ jobs:
     name: Check Formatting
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2.3.4
       - uses: volta-cli/action@v1
       - name: Get yarn cache directory path
         id: yarn-cache-dir-path
@@ -30,7 +30,7 @@ jobs:
     name: Test Broccoli Plugin
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2.3.4
       - uses: volta-cli/action@v1
       - name: Get yarn cache directory path
         id: yarn-cache-dir-path