[CODEOWNERS] Remove invalid owner (Azure#51678)

The focus of these changes is to address a linter failure where an owner recently lost permissions or group memberships and is no longer a valid owner.

Author: jsquire

.github/CODEOWNERS

@@ -1079,10 +1079,10 @@
 # ServiceOwners:                                                   @vipray-ms
 
 # PRLabel: %Nginx
-/sdk/nginx/Azure.ResourceManager.*/                                @jamesfan1 @bangbingsyb @spencerofwiti @amwaleh @briantkim93
+/sdk/nginx/Azure.ResourceManager.*/                                @jamesfan1 @bangbingsyb @spencerofwiti @amwaleh
 
 # ServiceLabel: %Nginx %Mgmt
-# ServiceOwners:                                                   @jamesfan1 @bangbingsyb @spencerofwiti @amwaleh @briantkim93
+# ServiceOwners:                                                   @jamesfan1 @bangbingsyb @spencerofwiti @amwaleh
 
 # PRLabel: %Operator Nexus - Network Cloud
 /sdk/networkcloud/Azure.ResourceManager.*/                         @Azure/azure-sdk-write-networkcloud