Remove unneeded versionadded directive

Author: javiereguiluz

string.rst

@@ -637,10 +637,6 @@ You can convert emojis to short codes with the ``emoji-text`` locale::
     $transliterator->transliterate('Breakfast with 🥝 or 🥛');
     // => 'Breakfast with :kiwifruit: or :milk-glass:
 
-.. versionadded:: 7.1
-
-    The ``text-emoji`` and ``emoji-text`` locales were introduced in Symfony 7.1.
-
 Removing Emojis
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