Builds test_utilities no matter BUILD_TESTING flag.

[francocipollone]

🦟 Bug fix

Summary

After making maliput::test_utilities agnostic of gtest there is no need to keep this guard
to avoid building this if not necessary

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if it affects the public API)

[codecov]

Codecov Report

Merging #612 (456f053) into main (5746a41) will increase coverage by 0.00%.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #612   +/-   ##
=======================================
  Coverage   85.69%   85.70%           
=======================================
  Files         232      232           
  Lines       10690    10690           
=======================================
+ Hits         9161     9162    +1     
+ Misses       1529     1528    -1     

see 1 file with indirect coverage changes