[drake_catkin_installed] Failing tests do not show up in CI

[nicolecheetham]

The catkin_installed tests are skipped due to requiring gtest which is unable to be found.

In the catkin_installed job, the build and test section has the CI green and passing despite the below warning. Skipped tests should instead result in the job failing causing the PR status to have a red X.

CMake Warning at /usr/share/catkin/cmake/test/gtest.cmake:159 (message):
  skipping gtest 'drake_catkin_installed_test' in project
  'drake_catkin_installed' because gtest was not found
Call Stack (most recent call first):
  /usr/share/catkin/cmake/test/gtest.cmake:89 (_catkin_add_executable_with_google_test)
  /usr/share/catkin/cmake/test/gtest.cmake:37 (_catkin_add_google_test)
  drake_catkin_installed/CMakeLists.txt:[54](https://github.com/RobotLocomotion/drake-external-examples/actions/runs/11486269912/job/31968186715?pr=330#step:5:55) (catkin_add_gtest)

Full log output