Replace asyncio.sleep with time.sleep in ChatFeed docs

[ahuang11]

Closes #7437

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.24%. Comparing base (26c2e7a) to head (c0e73bf).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7439      +/-   ##
==========================================
- Coverage   82.25%   82.24%   -0.01%     
==========================================
  Files         337      337              
  Lines       50678    50678              
==========================================
- Hits        41685    41681       -4     
- Misses       8993     8997       +4     

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