Remove unused cleanup code in endpointslice-controller

[XiShanYongYe-Chang]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

For cleanup part logic, it is used to protect the upgrade scenario, now we do not need it anymore.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[XiShanYongYe-Chang]

/cc @whitewindmills

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 28.21%. Comparing base (c8acebc) to head (81e30eb).

Files	Patch %	Lines
pkg/controllers/mcs/endpointslice_controller.go	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5148   +/-   ##
=======================================
  Coverage   28.21%   28.21%           
=======================================
  Files         632      632           
  Lines       43568    43557   -11     
=======================================
- Hits        12291    12288    -3     
+ Misses      30381    30371   -10     
- Partials      896      898    +2     

Flag	Coverage Δ
unittests	28.21% <0.00%> (+<0.01%)	⬆️

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[whitewindmills]

thanks
/lgtm
/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: whitewindmills

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