cleanup dead code of generating PropagationPolicy permanent id

[whitewindmills]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:
Since the PR(#4474) has been merged, we're going to remove those codes which generate policy permanent ID outside of webhook.
Same as #4928

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[whitewindmills]

/cc @RainbowMango

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 53.31%. Comparing base (b217a9c) to head (bfc0f6f).

Files	Patch %	Lines
pkg/detector/detector.go	0.00%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4949      +/-   ##
==========================================
+ Coverage   53.23%   53.31%   +0.07%     
==========================================
  Files         252      252              
  Lines       20514    20492      -22     
==========================================
+ Hits        10921    10925       +4     
+ Misses       8869     8844      -25     
+ Partials      724      723       -1     

Flag	Coverage Δ
unittests	53.31% <0.00%> (+0.07%)	⬆️

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[RainbowMango]

/assign

[XiShanYongYe-Chang]

Thanks a lot
/lgtm

[RainbowMango]

/approve

[karmada-bot]

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