refactor: revert fly.ai.toml rename, keep fly.toml for single app (#3855)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: yujonglee <yujonglee.dev@gmail.com>

Author: devin-ai-integration[bot]

.github/workflows/api_cd.yaml

@@ -27,7 +27,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: superfly/flyctl-actions/setup-flyctl@master
-      - run: flyctl deploy --config apps/api/fly.ai.toml --dockerfile apps/api/Dockerfile --remote-only --build-arg APP_VERSION=${{ needs.compute-version.outputs.version }}
+      - run: flyctl deploy --config apps/api/fly.toml --dockerfile apps/api/Dockerfile --remote-only --build-arg APP_VERSION=${{ needs.compute-version.outputs.version }}
         env:
           FLY_API_TOKEN: ${{ secrets.FLY_API_TOKEN }}