Update CHANGELOG.md (#2876)

Update changelog to account for dropped support of Kinematics of External Loads.

Author: aymanhab

CHANGELOG.md

@@ -32,7 +32,7 @@ v4.2
   - This improves the performance of component-heavy models by ~5-10 %
   - The behavior and interface of `ComponentPath` should remain the same
 - The new Matlab CustomStaticOptimization.m guides the user to build their own custom static optimization code. 
-
+- Dropped support for separate Kinematics for application of External Loads. ([PR #2770] (https://github.com/opensim-org/opensim-core/pull/2770)). 
 
 v4.1
 ====