Clarify README backend URL documentation for deployment contexts (#2578)

* Update README

Updated README

* Initial plan

* Update README comment to reflect deployment URLs

Co-authored-by: Keeeeeeeks <16293980+Keeeeeeeks@users.noreply.github.com>

---------

Co-authored-by: Keeks <Keeeeeeeks@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Keeeeeeeks <16293980+Keeeeeeeks@users.noreply.github.com>
Co-authored-by: Piyal Basu <pbasu235@gmail.com>

Author: 3 people

README.md

@@ -50,7 +50,7 @@ INDEXER_V2_URL=your_backend_v2_prod_url_here
 
 ```
 
-These URLs point to the production Freighter backend. For more details on
+These URLs should point to your deployment of Freighter backend. For more details on
 backend configuration, see
 [extension/README.md](extension/README.md#configure-the-backend).