fix(deps): update dependency postcss to ^8.5.15 (#5940)

Co-authored-by: homarr-renovate[bot] <158783068+homarr-renovate[bot]@users.noreply.github.com>

apps/docs/package.json

@@ -37,7 +37,7 @@
     "dayjs": "catalog:",
     "docusaurus-plugin-image-zoom": "^3.0.1",
     "leader-line-new": "^1.1.9",
-    "postcss": "^8.5.10",
+    "postcss": "^8.5.15",
     "posthog-docusaurus": "^2.0.5",
     "prism-react-renderer": "^2.4.1",
     "random-word-slugs": "^0.1.7",