Remove DEBUG from kafka::clients::Config

Author: kenneth-jia

include/kafka/ClientConfig.h

@@ -71,11 +71,6 @@ class Config: public Properties
      */
     static const constexpr char* LOG_LEVEL                 = "log_level";
 
-    /**
-     * A comma-separated list of debug contexts to enable.
-     */
-    static const constexpr char* DEBUG                     = "debug";
-
     /**
      * Timeout for network requests.
      * Default value: 60000