fix(frontend): server metrics look strange after reload

[zyoshoka]

What

サーバーメトリクスが2つ以上あるとリロード直後の表示がおかしくなる問題を修正します。

Why

Closes #14463

Additional info (optional)

Checklist

• [x] Read the contribution guide
• [x] Test working in a local environment
• [ ] (If needed) Add story of storybook
• [x] (If needed) Update CHANGELOG.md
• [ ] (If possible) Add tests

[codecov[bot]]

Codecov Report

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

Project coverage is 20.02%. Comparing base (44f6216) to head (913c23b). Report is 7 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ges/frontend/src/widgets/server-metric/cpu-mem.vue	0.00%	1 Missing :warning:
...ackages/frontend/src/widgets/server-metric/net.vue	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #14467 +/- ## =========================================== - Coverage 20.21% 20.02% -0.19% =========================================== Files 725 725 Lines 100550 100550 Branches 1050 1052 +2 =========================================== - Hits 20327 20137 -190 - Misses 79681 79869 +188 - Partials 542 544 +2 ```

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[syuilo]

🙏🏿