[doc] skip doctests of removed C++ modules

4 jobs for remove-cpp in 9 minutes (queued for 3 seconds)
Name Stage Failure
failed
build_macos_intel_39 Build
    raise RuntimeError("Solver could not find solution.")
RuntimeError: Solver could not find solution.
Uploading artifacts for failed job
Uploading artifacts...
Runtime platform
arch=amd64 os=darwin pid=75937 revision=4b9e985a version=14.4.0
WARNING: coverage.xml: no matching files
ERROR: No files to upload
Cleaning up project directory and file based variables
ERROR: Job failed: exit status 1

failed
build_linux_39 Build
  File "/scratch/builds/bob/bob.learn.em/miniconda/lib/python3.9/site-packages/boa/core/solver.py", line 200, in solve
raise RuntimeError("Solver could not find solution.")
RuntimeError: Solver could not find solution.
Uploading artifacts for failed job
Uploading artifacts...
WARNING: coverage.xml: no matching files
ERROR: No files to upload
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1