docs: improve the description of cp

[wangxiaoxuan273]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #1456

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.78%. Comparing base (d1fe4d0) to head (12dfe5f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1498   +/-   ##
=======================================
  Coverage   85.78%   85.78%           
=======================================
  Files         116      116           
  Lines        4059     4059           
=======================================
  Hits         3482     3482           
  Misses        345      345           
  Partials      232      232           

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[shizhMSFT]

LGTM