Remove outdated doc section about custom clients

Author: SergeyRyabinin

docs/CMake_Parameters.md

@@ -10,12 +10,6 @@ Example:
 -DBUILD_ONLY="s3;dynamodb;cognito-identity"
 ```
 
-### ADD_CUSTOM_CLIENTS
-Allows you to build any arbitrary clients based on the api definition. Simply place your definition in the code-generation/api-definitions folder. Then pass this arg to cmake. The cmake configure step will generate your client and include it as a subdirectory in your build. This is particularly useful if you want to generate a C++ client for using one of your API Gateway services. To use this feature you need to have python 2.7, java, jdk1.8, and maven installed and in your executable path. Example:
-```sh
--DADD_CUSTOM_CLIENTS="serviceName=myCustomService, version=2015-12-21;serviceName=someOtherService, version=2015-08-15"
-```
-
 ### REGENERATE_CLIENTS
 This argument will wipe out all generated code and generate the client directories from the code-generation/api-definitions folder. To use this argument, you need to have python 2.7, java, jdk1.8, and maven installed in your executable path. Example:
 ```sh