Fix debug when using CLI as library

When CLI is used as a library, the method for debug returns incorrect result - previously the return type of the method we are calling was `string[]`, we've changed it to `string` but forgot to remove the `_.first(result)`.
So now the debug returns incorrect URL. Remove the `_.first` and return the result directly.

lib/services/debug-service.ts

@@ -64,7 +64,7 @@ export class DebugService extends EventEmitter implements IDebugService {
 			result = await debugService.debug(debugData, debugOptions);
 		}
 
-		return _.first(result);
+		return result;
 	}
 
 	public getDebugService(device: Mobile.IDevice): IPlatformDebugService {