chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/kotlin.yml

@@ -4,7 +4,7 @@ jobs:
   build-test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-java@v4
         with:

.github/workflows/php.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
 
     - name: Setup PHP
       uses: shivammathur/setup-php@v2

.github/workflows/python.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
 
     - name: Set up Python
       uses: actions/setup-python@v5