chore(deps): update dependency postcss to v8.4.2 (#1093)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [postcss](https://postcss.org/) ([source](https://github.com/postcss/postcss)) | devDependencies | patch | [`8.4.1` -> `8.4.2`](https://renovatebot.com/diffs/npm/postcss/8.4.1/8.4.2) |

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### Release Notes

<details>
<summary>postcss/postcss</summary>

### [`v8.4.2`](https://github.com/postcss/postcss/blob/master/CHANGELOG.md#&#8203;842)

[Compare Source](https://github.com/postcss/postcss/compare/8.4.1...8.4.2)

-   Fixed previous source map support in zero plugins mode.

</details>

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### Configuration

📅 **Schedule**: At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

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 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box.

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This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).

Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/1093
Co-authored-by: renovate <renovatebot@kolaente.de>
Co-committed-by: renovate <renovatebot@kolaente.de>

package.json

@@ -76,7 +76,7 @@
     "faker": "5.5.3",
     "jest": "27.3.1",
     "netlify-cli": "8.0.3",
-    "postcss": "8.4.1",
+    "postcss": "8.4.2",
     "postcss-preset-env": "7.0.1",
     "rollup": "2.60.1",
     "rollup-plugin-visualizer": "5.5.2",