chore(deps): update dependency postcss to v8.4.1 (#1083)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [postcss](https://postcss.org/) ([source](https://github.com/postcss/postcss)) | devDependencies | patch | [`8.4.0` -> `8.4.1`](https://renovatebot.com/diffs/npm/postcss/8.4.0/8.4.1) |

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### Release Notes

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

### [`v8.4.1`](https://github.com/postcss/postcss/blob/master/CHANGELOG.md#&#8203;841)

[Compare Source](https://github.com/postcss/postcss/compare/8.4.0...8.4.1)

-   Fixed `Stringifier` types (by James Garbutt).

</details>

---

### 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.

---

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

---

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

Reviewed-on: vikunja/frontend#1083
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": "8.0.1",
-    "postcss": "8.4.0",
+    "postcss": "8.4.1",
     "postcss-preset-env": "7.0.1",
     "rollup": "2.60.1",
     "rollup-plugin-visualizer": "5.5.2",

yarn.lock

@@ -11399,10 +11399,10 @@ postcss-values-parser@^2.0.1:
     indexes-of "^1.0.1"
     uniq "^1.0.1"
 
-postcss@8.4.0:
-  version "8.4.0"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.0.tgz#cd4c33af00a00ba93ccf6ae1219f57c5e5ab5234"
-  integrity sha512-BRMNx3Wy7UI89jN8H4ZVS5lQMPM2OSMkOkvDCSjwXa7PWTs24k7Lm55NXLbMbs070LvraXaxN5l1npSOS6wMVw==
+postcss@8.4.1:
+  version "8.4.1"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.1.tgz#73051f825509ad1a716ef500108001bf3d1fa8f7"
+  integrity sha512-WqLs/TTzXdG+/A4ZOOK9WDZiikrRaiA+eoEb/jz2DT9KUhMNHgP7yKPO8vwi62ZCsb703Gwb7BMZwDzI54Y2Ag==
   dependencies:
     nanoid "^3.1.30"
     picocolors "^1.0.0"