chore: reuse proxyutil import for proxy

[a7i]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:
remove extra import and reuse proxyutil

Which issue(s) this PR fixes:
N/A

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-commenter]

Codecov Report

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

Project coverage is 53.12%. Comparing base (167f213) to head (2f3ac7d).

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

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4906      +/-   ##
==========================================
- Coverage   53.13%   53.12%   -0.01%     
==========================================
  Files         251      251              
  Lines       20415    20415              
==========================================
- Hits        10848    10846       -2     
- Misses       8853     8855       +2     
  Partials      714      714              

Flag	Coverage Δ
unittests	53.12% <0.00%> (-0.01%)	⬇️

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[zhzhuang-zju]

/lgtm

[RainbowMango]

/lgtm
/assign @chaunceyjiang

[liangyuanpeng]

/lgtm

[RainbowMango]

/assign @whitewindmills
as well

[chaunceyjiang]

Thanks~

/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chaunceyjiang

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