Update CHANGELOG.md.

Author: chrisdembia

CHANGELOG.md

@@ -211,6 +211,8 @@ programmatically in MATLAB or python.
   its properties are updated during scaling. (PR #1994)
 - The source code for the "From the Ground Up: Building a Passive Dynamic
   Walker Example" was added to this repository.
+- OpenSim no longer looks for the simbody-visualizer using the environment
+  variable `OPENSIM_HOME`.
 
 Documentation
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