Revert "[clang][Modules] Remove a resloved issue from StandardCPlusPlusModules.rst"

This reverts commit 82dc2d4.

The fix has been reverted in f63e8ed

Author: hokein

clang/docs/StandardCPlusPlusModules.rst

@@ -1378,6 +1378,14 @@ merging happening in the semantic analyzer. This is due to a divergence in the
 implementation path. This is tracked by
 `#61465 <https://github.com/llvm/llvm-project/issues/61465>`_.
 
+Ignored ``preferred_name`` Attribute
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When Clang writes BMIs, it will ignore the ``preferred_name`` attribute on
+declarations which use it. Thus, the preferred name will not be displayed in
+the debugger as expected. This is tracked by
+`#56490 <https://github.com/llvm/llvm-project/issues/56490>`_.
+
 Don't emit macros about module declaration
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~