Remove C build references from CMakeLists.txt

tutorials/ros_unity_integration/ros2_packages/unity_robotics_demo_msgs/CMakeLists.txt

 cmake_minimum_required(VERSION 3.5)
 project(unity_robotics_demo_msgs)
 
-# Default to C99
-if(NOT CMAKE_C_STANDARD)
-  set(CMAKE_C_STANDARD 99)
-endif()
-
-# Default to C++14
-if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 14)
-endif()
-
-if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-  add_compile_options(-Wall -Wextra -Wpedantic)
-endif()
-
-find_package(ament_cmake REQUIRED)
 find_package(rosidl_default_generators REQUIRED)
 find_package(builtin_interfaces REQUIRED)
 find_package(geometry_msgs REQUIRED)