labels cannot be deleted via Karmada propagation

[whitewindmills]

What type of PR is this? /kind bug

What this PR does / why we need it:

Which issue(s) this PR fixes: Fixes #4781

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

karmada-controller-manager: Fix the problem that labels cannot be deleted via Karmada propagation.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 51.77%. Comparing base (6534ffb) to head (ce84edf).

Files	Patch %	Lines
pkg/util/helper/work.go	0.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #4784 +/- ## ========================================== + Coverage 51.76% 51.77% +0.01% ========================================== Files 250 250 Lines 24980 24980 ========================================== + Hits 12930 12933 +3 + Misses 11340 11338 -2 + Partials 710 709 -1 ``` | [Flag](https://app.codecov.io/gh/karmada-io/karmada/pull/4784/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=karmada-io) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/karmada-io/karmada/pull/4784/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=karmada-io) | `51.77% <80.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=karmada-io#carryforward-flags-in-the-pull-request-comment) to find out more.

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[XiShanYongYe-Chang]

Thanks~ /assign

[XiShanYongYe-Chang]

@whitewindmills can you help add the release-note?

[whitewindmills]

@XiShanYongYe-Chang done.

[XiShanYongYe-Chang]

/assign @RainbowMango

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RainbowMango

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Needs approval from an approver in each of these files: - ~~[pkg/util/OWNERS](https://github.com/karmada-io/karmada/blob/master/pkg/util/OWNERS)~~ [RainbowMango] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment