Bump actions/checkout from 1 to 2.3.4

Bumps [actions/checkout](https://github.com/actions/checkout) from 1 to 2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v1...v2.3.4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/lint.yml

@@ -17,7 +17,7 @@ jobs:
 
     name: php${{ matrix.php-versions }} lint
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - name: Set up php${{ matrix.php-versions }}
         uses: shivammathur/setup-php@2.11.0
         with:
@@ -31,7 +31,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@master
+      uses: actions/checkout@v2.3.4
     - name: Set up php
       uses: shivammathur/setup-php@2.11.0
       with:
@@ -50,7 +50,7 @@ jobs:
         node-version: [14.x]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - name: Use node ${{ matrix.node-version }}
         uses: actions/setup-node@v1
         with:
@@ -71,7 +71,7 @@ jobs:
 
     name: stylelint node${{ matrix.node-versions }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
 
       - name: Set up node ${{ matrix.node-versions }}
         uses: actions/setup-node@v1