Update com.unity.perception/CHANGELOG.md

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Co-authored-by: jhogins <jon.hogins@gmail.com>

com.unity.perception/CHANGELOG.md

 
 ### Changed
 
-Renamed all instances of "KeyPoint" to "Keypoint" for standards adherence.
+Renamed all types and members named "KeyPoint" to "Keypoint"
 
 ### Deprecated