Update maven.yml

Author: Allen-Chen-BU

.github/workflows/maven.yml

@@ -28,6 +28,7 @@ jobs:
         distribution: 'temurin'
         cache: maven
     - name: Build with Maven
+      working-directory: ./code/backend
       run: mvn -B package --file pom.xml
 
     # Optional: Uploads the full dependency graph to GitHub to improve the quality of Dependabot alerts this repository can receive