[Identity] - Remove await from README (Azure#14651)

This small PR just removes an `await` call that doesn't make sense outside of async functions. Using a client is also not necessary to demonstrate how to create one.

Resolves Azure#14002

Author: maorleger

sdk/identity/identity/README.md

@@ -139,9 +139,6 @@ const credential = new DefaultAzureCredential();
 
 // Create authenticated client
 const client = new KeyClient(vaultUrl, credential);
-
-// Use service from authenticated client
-const getResult = await client.getKey("MyKeyName");
 ```
 
 ### Specifying a user assigned managed identity with the `DefaultAzureCredential`