ci: update actions/checkout to v6

Author: stklcode

.github/workflows/tests.yml

@@ -4,7 +4,7 @@ jobs:
   quality:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:

.github/workflows/wordpress-plugin-asset-update.yml

@@ -8,7 +8,7 @@ jobs:
     name: Push to master
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: WordPress.org plugin asset/readme update
       uses: 10up/action-wordpress-plugin-asset-update@stable
       env:

.github/workflows/wordpress-plugin-check.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Package plugin
         run: |

.github/workflows/wordpress-plugin-deploy.yml

@@ -9,7 +9,7 @@ jobs:
     name: New tag
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: WordPress Plugin Deploy
       uses: 10up/action-wordpress-plugin-deploy@stable
       env: