Removed Object Metadata from Concepts Overview. (kubernetes#17691)

`Object Metadata` section is misleading, as the Concept's overview is covering what master and non-master nodes are and list of objects. But there is no discussion on `Object Metadata` till the end and all of sudden there is Object Metadata section with no background introduction or definition, and just a reference to `Annotations` which is confusing if you read the content from the beginning. So it would be better to remove this as it is covered later here `https://kubernetes.io/docs/concepts/overview/working-with-objects/annotations/`.

content/en/docs/concepts/_index.md

@@ -59,10 +59,6 @@ The Kubernetes master is responsible for maintaining the desired state for your
 
 The nodes in a cluster are the machines (VMs, physical servers, etc) that run your applications and cloud workflows. The Kubernetes master controls each node; you'll rarely interact with nodes directly.
 
-#### Object Metadata
-
-
-* [Annotations](/docs/concepts/overview/working-with-objects/annotations/)
 
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