[extension/zpages] document unsupported none level

[codeboten]

Fix #10965

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.22%. Comparing base (7da6b61) to head (62d658d).
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11016      +/-   ##
==========================================
+ Coverage   92.03%   92.22%   +0.19%     
==========================================
  Files         412      408       -4     
  Lines       19313    19126     -187     
==========================================
- Hits        17774    17639     -135     
+ Misses       1185     1126      -59     
- Partials      354      361       +7     

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