Remove extra find_package(ament_cmake_gtest).

nuclearsandwich · nuclearsandwich · commit 695ad836f645 · 2018-12-05T12:58:11.000-08:00
This package should only be needed if BUILD_TESTING is on and is
find_package'd below if ament_cmake is found and BUILD_TESTING is on.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -44,8 +44,6 @@ endif()
 find_package(ament_cmake QUIET)
 
 if ( ament_cmake_FOUND )
-  find_package(ament_cmake_gtest REQUIRED)
-
   # Not adding -DUSING_ROS since xml_parsing.cpp hasn't been ported to ROS2
 
   message(STATUS "------------------------------------------")
