chore(deps): update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/check-urls.yml

@@ -19,7 +19,7 @@ jobs:
         working-directory: ./check_urls
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Dart
         uses: dart-lang/setup-dart@v1.4
@@ -41,7 +41,7 @@ jobs:
       run:
         working-directory: ./example
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Dart
         uses: dart-lang/setup-dart@v1.4

.github/workflows/dart.yml

@@ -24,7 +24,7 @@ jobs:
         rxdart: [ not_override ]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Dart
         uses: dart-lang/setup-dart@v1.4