Bump actions/checkout from 2 to 2.3.4 (#12)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v2.3.4)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/docker.build.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       -
         name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v2.3.4
       -
         name: Docker meta
         id: docker_meta

.github/workflows/docker.lint.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps: 
     - name: Checkout
-      uses: actions/checkout@master
+      uses: actions/checkout@v2.3.4
     - name: lint
       uses: luke142367/Docker-Lint-Action@v1.1.1
       with: