ci: Update flutter-ci.yml

Author: phanatagama

.github/workflows/flutter-ci.yml

@@ -75,5 +75,5 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with:
           tag_name: ${{ steps.tag.outputs.release_tag }}
-          files: build/app/outputs/apk/release/app-release.apk
+          files: ./build/app/outputs/apk/release/app-release.apk