Fix typo in CHANGELOG.md

CHANGELOG.md

@@ -66,7 +66,7 @@ Thankyou! -->
     * _**(New)**_ Event class-specific attributes using `observable` property class's attributes. This allows defining class attributes as observables _only_ within instances of this specific class.
     * _**(New)**_ Event class-specific attribute _paths_ using top-level `observables` property. The `observables` property holds an object mapping from an dotted attribute path to an observable `type_id`. This allows defining an observables _only_ within instances of this specific class, and only for the attributes at these paths, even for attributes that are within nested objects and arrays. This can also be used for top-level class attributes, which can be more convenient that defining a class attribute observable for classes that extend another, but don't otherwise change a attribute definition.
 3. Metaschema improvements. #993 
-    * Detect expected top-level properties in object and event class definitions. This was added at this point to detects invalid observable definitions: invalid `observable` property in event classes, and invalid `observables` property in objects.
+    * Detect expected top-level properties in object and event class definitions. This was added at this point to detect invalid observable definitions: invalid `observable` property in event classes, and invalid `observables` property in objects.
     * Remove hard-coded list of categories from `metaschema/categories.schema.json`, leaving this to the `ocsf-validator`. This change makes testing with alternate schemas that may add extra categories easier, as well as making it possible to validate private extensions that contain new categories.
 
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