doc/rl-2511: note removal of llvmPackages from haskell.packages.*

This should be the only observable breakage from #441101 /
921f5db.

Author: sternenseemann

doc/release-notes/rl-2511.section.md

@@ -34,6 +34,12 @@
   The latter was probably broken anyway.
   If there is interest in restoring support for these architectures, it should be possible to cross‐compile a bootstrap GHC binary.
 
+- `haskellPackages` and the package sets under `haskell.packages` no longer expose an `llvmPackages` attribute,
+  though it can still be accessed via `ghc.llvmPackages` (from the same package set).
+  Haskell packages usually only need to depend on an LLVM version matching GHC if they force the use the LLVM
+  backend even if NCG is available. In this case, it is best to use the `forceLlvmCodegenBackend` helper.
+  In all other cases, like linking against `libLLVM`, Haskell packages should use the appropriate version of `llvmPackages` from `pkgs`.
+
 - `base16-builder` node package has been removed due to lack of upstream maintenance.
 
 - `python3Packages.bjoern` has been removed, as the upstream is unmaintained and it depends on a 14-year-old version of http-parser with numerous vulnerabilities.