Update index.rst

The section "Backward Compatibility promise" is written twice

Author: Ldiro

src/Turbo/Resources/doc/index.rst

@@ -785,16 +785,6 @@ Credits
 Symfony UX Turbo has been created by `Kévin Dunglas`_. It has been inspired by
 `hotwired/turbo-rails`_ and `sroze/live-twig`_.
 
-Backward Compatibility promise
-------------------------------
-
-This bundle aims at following the same Backward Compatibility promise as
-the Symfony framework:
-https://symfony.com/doc/current/contributing/code/bc.html
-
-However it is currently considered `experimental`_,
-meaning it is not bound to Symfony's BC policy for the moment.
-
 .. _`Hotwire Turbo`: https://turbo.hotwired.dev
 .. _`the Symfony UX initiative`: https://symfony.com/ux
 .. _`Single Page Apps`: https://en.wikipedia.org/wiki/Single-page_application