Update actions/checkout action to v4 (#82)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/build.yml

@@ -16,7 +16,7 @@ jobs:
     steps:
       # Checkout the repo
       - name: 'Checkout'
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 

.github/workflows/docker.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: "Checkout source code at current commit"
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
     - name: Prepare tags for Docker image
       if: (github.event_name == 'release' && github.event.action == 'created') || github.event.pull_request.head.repo.full_name == github.repository
       id: prepare

.github/workflows/validate-codeowners.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: "Checkout source code at current commit"
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       # Leave pinned at 0.7.1 until https://github.com/mszostok/codeowners-validator/issues/173 is resolved
     - uses: mszostok/[email protected]
       if: github.event.pull_request.head.repo.full_name == github.repository