docs: note route group callback type fix in changelog

Author: maniaba

user_guide_src/source/changelogs/v4.7.6.rst

@@ -33,6 +33,9 @@ Bugs Fixed
 **********
 
 - **Commands:** Fixed a bug where generator commands did not sort the imports of a template with CRLF line endings.
+- **Routing:** Corrected the PHPDoc callback type of ``RouteCollection::group()``
+  to preserve the concrete collection type, allowing callbacks typed to a
+  ``RouteCollection`` subclass to pass static analysis.
 - **Format:** Fixed ``XMLFormatter`` so that an array key that becomes empty after
   sanitization no longer triggers a ``ValueError``; the fallback tag name ``item``
   is used instead. Values that cannot be converted to a string, such as objects