Remove scikit-build from dependency list

[vyasr]

Description

This dependency shouldn't be necessary, all of our tests of rapids-cython[-core] just spoof that they're being run via the Python interface while actually running as raw CMake.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• The cmake-format.json is up to date with these changes.
• I have added new files under rapids-cmake/
  • I have added include guards (include_guard(GLOBAL))
  • I have added the associated docs/ rst file and update the api.rst

[bdice]

/merge