Mention #91 in the CHANGELOG

CHANGELOG.markdown

+next [????.??.??]
+-----------------
+* On pre-8.0 GHCs, drop the `call-stack` dependency. This dependency was
+  introduced in `exceptions-0.10.6`, but it induced breakage in libraries
+  that derived instances of `MonadThrow`, `MonadCatch`, or `MonadMask` for
+  newtypes without first enabling `ConstraintKinds` and `FlexibleContexts`.
+  (Later versions of GHC do not require these language extensions for derived
+  instances, so only old GHCs were affected.) To avoid breakage, `exceptions`
+  no longer uses `HasCallStack` constraints on pre-8.0 versions of GHC.
+
+  Note that `exceptions` still uses `HasCallStack` constraints on GHC 8.0 and
+  later, and as a result, these versions of GHC are unaffected by this change.
+
 0.10.6 [2022.11.30]
 -------------------
 * The class methods and functions in `Control.Monad.Catch` now have