fix: custom copilot ClientCitation error

[kuojianlu]

Fix https://msazure.visualstudio.com/Microsoft%20Teams%20Extensibility/_workitems/edit/30469033

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.04%. Comparing base (8d6d360) to head (39b8510).
Report is 12 commits behind head on release/5.12.

Additional details and impacted files

@@               Coverage Diff                @@
##           release/5.12   #12884      +/-   ##
================================================
+ Coverage         90.02%   90.04%   +0.02%     
================================================
  Files               576      576              
  Lines             34185    34196      +11     
  Branches           6656     6866     +210     
================================================
+ Hits              30774    30792      +18     
+ Misses             1507     1501       -6     
+ Partials           1904     1903       -1     

see 4 files with indirect coverage changes