Update src/typing_extensions.py

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Author: JelleZijlstra

src/typing_extensions.py

@@ -321,6 +321,7 @@ class Other(Leaf):  # Error reported by type checker
 else:
     def solid_base(cls):
         """This decorator marks a class a solid base.
+
         Child classes of a solid base cannot inherit from other solid bases that are
         not parent classes of the solid base.