Added tests for remediation controller

[anujagrawal699]

Description:
This PR enhances the unit tests for the Remedy Controller in the remediation package. The improvements aim to increase code reliability, maintainability, and test coverage for the Remedy Controller.

Additions and Modifications:

1. pkg/controllers/remediation/remedy_controller_test.go

Test Coverage:

1. remedy_controller_test.go: 0% to 74.4%

Overall coverage of remediation controller: 68.82% to 86.5%

What type of PR is this?
/kind failing-test
/kind feature

Which issue(s) this PR fixes:
Fixes a part of #5470

Does this PR introduce a user-facing change?:

NONE

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 34.94%. Comparing base (721107d) to head (270819a).
Report is 12 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5595      +/-   ##
==========================================
+ Coverage   34.87%   34.94%   +0.06%     
==========================================
  Files         645      645              
  Lines       44833    44833              
==========================================
+ Hits        15637    15665      +28     
+ Misses      27991    27956      -35     
- Partials     1205     1212       +7     

Flag	Coverage Δ
unittests	34.94% <ø> (+0.06%)	⬆️

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[XiShanYongYe-Chang]

/lgtm
/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: XiShanYongYe-Chang

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• pkg/controllers/OWNERS [XiShanYongYe-Chang]

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