ci: update working directory for backend steps

.gitea/workflows/ci.yml

@@ -12,9 +12,8 @@ jobs:
     steps:
       - name: "Checkout"
         uses: actions/checkout@v3
-      - name: "Go to backend"
-        run: cd backend
       - uses: actions/cache@v3
+        working-directory: ./backend
         with:
           path: |
             ~/.gradle/caches
@@ -23,10 +22,13 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-gradle-
       - name: "Prepare Gradle"
+        working-directory: ./backend
         run: gradle clean
       - name: "Check"
+        working-directory: ./backend
         run: gradle check
       - name: "Stop Gradle"
+        working-directory: ./backend
         run: gradle --stop
 
   eslint: