chore(deps): update dependency postcss to v8.4.39 (#323)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [postcss](https://postcss.org/)
([source](https://github.com/postcss/postcss)) | [`8.4.38` ->
`8.4.39`](https://renovatebot.com/diffs/npm/postcss/8.4.38/8.4.39) |
[![age](https://developer.mend.io/api/mc/badges/age/npm/postcss/8.4.39?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/npm/postcss/8.4.39?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/npm/postcss/8.4.38/8.4.39?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/postcss/8.4.38/8.4.39?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>postcss/postcss (postcss)</summary>

###
[`v8.4.39`](https://github.com/postcss/postcss/blob/HEAD/CHANGELOG.md#8439)

[Compare
Source](https://github.com/postcss/postcss/compare/8.4.38...8.4.39)

- Fixed `CssSyntaxError` types (by
[@&#8203;romainmenke](https://github.com/romainmenke)).

</details>

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app/package.json

@@ -36,7 +36,7 @@
     "autoprefixer": "10.4.19",
     "eslint": "8.57.0",
     "eslint-config-next": "14.2.4",
-    "postcss": "8.4.38",
+    "postcss": "8.4.39",
     "prettier": "3.3.2",
     "prettier-plugin-organize-imports": "3.2.4",
     "prettier-plugin-tailwindcss": "0.6.3",