docs: switch quickstart note to warning

[nodegard]

Description

Please describe the change you have made.

Checklist:

• Tests added/updated.
• Documentation updated. Documentation is generated from docstrings - these must be updated according to your change.
  If a new method has been added it should be referenced in cognite.rst in order to generate docs based on its docstring.
• Changelog updated in CHANGELOG.md.
• Version bumped. If triggering a new release is desired, bump the version number in _version.py and pyproject.toml per semantic versioning.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.72%. Comparing base (8a8ed12) to head (113726e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1912      +/-   ##
==========================================
- Coverage   90.72%   90.72%   -0.01%     
==========================================
  Files         130      130              
  Lines       20139    20139              
==========================================
- Hits        18272    18271       -1     
- Misses       1867     1868       +1     

see 1 file with indirect coverage changes