The test coverage_tests::cover_tests keeps timing out.

[1uc]

I find myself rerunning test regularly. Often it's because one of the ctest tests timed out after 300s.

A recent case is:

195/195 Test  #18: coverage_tests::cover_tests ..............................................***Timeout 300.18 sec

https://github.com/neuronsimulator/nrn/actions/runs/6046601028/job/16408450820?pr=2445#step:18:3996

While is should normally run too quickly to blame flake server performance:

         Start  22: coverage_tests::cover_tests
 75/277 Test  #22: coverage_tests::cover_tests ..............................................   Passed    2.58 sec

https://github.com/neuronsimulator/nrn/actions/runs/6046601028/job/16408452047?pr=2445#step:18:5347