Bump actions/checkout from v2 to v2.3.0

Bumps [actions/checkout](https://github.com/actions/checkout) from v2 to v2.3.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/master/CHANGELOG.md)
- [Commits](actions/checkout@v2...b4483ad)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/docker-build.yml

@@ -6,7 +6,7 @@ jobs:
     if: '!github.event.deleted'
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v2.3.0
     - name: Build and push Docker images
       uses: docker/[email protected]
       with:

.github/workflows/pull_request.yml

@@ -5,7 +5,7 @@ jobs:
     name: Hadolint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.0
       - name: hadolint
         uses: reviewdog/action-hadolint@v1
         with: