Update actions/checkout action to v4

.gitea/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
     env:
       working_directory: "./src"
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Set up Go
         uses: actions/setup-go@v2
@@ -35,7 +35,7 @@ jobs:
     env:
       working_directory: "./client"
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Setup Node.js environment
         uses: actions/setup-node@v2.5.2