fix: use update instead of patch to set pod's role

[xuriwuyun]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.

Project coverage is 64.55%. Comparing base (8cf92c7) to head (e011386).

Files with missing lines	Patch %	Lines
...g/controller/instanceset/pod_role_event_handler.go	77.77%	2 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release-0.9    #8871      +/-   ##
===============================================
+ Coverage        64.40%   64.55%   +0.14%     
===============================================
  Files              359      359              
  Lines            46457    46457              
===============================================
+ Hits             29922    29989      +67     
+ Misses           13841    13787      -54     
+ Partials          2694     2681      -13     

Flag	Coverage Δ
unittests	64.55% <77.77%> (+0.14%)	⬆️

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