chore: don't set placement annotation if no multi-cluster configured

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 27.27273% with 8 lines in your changes missing coverage. Please review.

Project coverage is 64.52%. Comparing base (95bf118) to head (be008b3). Report is 8 commits behind head on main.

Files	Patch %	Lines
controllers/apps/transformer_component_workload.go	16.66%	4 Missing and 1 partial :warning:
pkg/controller/component/component.go	40.00%	2 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #7677 +/- ## ========================================== - Coverage 64.57% 64.52% -0.05% ========================================== Files 339 339 Lines 42196 42210 +14 ========================================== - Hits 27247 27235 -12 - Misses 12567 12597 +30 + Partials 2382 2378 -4 ``` | [Flag](https://app.codecov.io/gh/apecloud/kubeblocks/pull/7677/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apecloud) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/apecloud/kubeblocks/pull/7677/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apecloud) | `64.52% <27.27%> (-0.05%)` | :arrow_down: | 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=apecloud#carryforward-flags-in-the-pull-request-comment) to find out more.

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[leon-inf]

/cherry-pick release-0.9

[github-actions[bot]]

🤖 says: cherry pick action finished successfully 🎉!
See: https://github.com/apecloud/kubeblocks/actions/runs/9756439072