relnotes: Remove note about -split-sections on Windows

Split-sections unfortunately isn't yet working.

docs/users_guide/8.4.1-notes.rst

@@ -254,9 +254,6 @@ Compiler
   performance for recursive types not shaped like cons-lists, and allows ``null``
   to terminate for more (but not all) infinitely large structures.
 
-- :ghc-flag:`-fsplit-sections` is now supported on x86_64 Windows and is on by default.
-  See :ghc-ticket:`12913`.
-
 - Configure on Windows now supports the ``--enable-distro-toolchain``
   ``configure`` flag, which can be used to build a GHC using compilers on your
   ``PATH`` instead of using the bundled bindist. See :ghc-ticket:`13792`