Fix grammar

Author: mmynk

content/en/docs/reference/glossary/object.md

@@ -4,7 +4,7 @@ id: object
 date: 2020-10-12
 full_link: /docs/concepts/overview/working-with-objects/#kubernetes-objects
 short_description: >
-   A entity in the Kubernetes system, representing part of the state of your cluster.
+   An entity in the Kubernetes system, representing part of the state of your cluster.
 aka: 
 tags:
 - fundamental