build(deps-dev): bump postcss from 8.4.25 to 8.4.26 in /frontend

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.25 to 8.4.26.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.4.25...8.4.26)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

frontend/package-lock.json

@@ -54,7 +54,7 @@
         "eslint-plugin-import": "^2.27.5",
         "eslint-plugin-matrix-org": "^1.2.0",
         "eslint-plugin-prettier": "^4.2.1",
-        "postcss": "^8.4.25",
+        "postcss": "^8.4.26",
         "prettier": "2.8.0",
         "react-test-renderer": "^18.2.0",
         "rimraf": "^5.0.1",
@@ -17139,9 +17139,9 @@
       }
     },
     "node_modules/postcss": {
-      "version": "8.4.25",
-      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.25.tgz",
-      "integrity": "sha512-7taJ/8t2av0Z+sQEvNzCkpDynl0tX3uJMCODi6nT3PfASC7dYCWV9aQ+uiCf+KBD4SEFcu+GvJdGdwzQ6OSjCw==",
+      "version": "8.4.26",
+      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.26.tgz",
+      "integrity": "sha512-jrXHFF8iTloAenySjM/ob3gSj7pCu0Ji49hnjqzsgSRa50hkWCKD0HQ+gMNJkW38jBI68MpAAg7ZWwHwX8NMMw==",
       "dev": true,
       "funding": [
         {

frontend/package.json

@@ -61,7 +61,7 @@
     "eslint-plugin-import": "^2.27.5",
     "eslint-plugin-matrix-org": "^1.2.0",
     "eslint-plugin-prettier": "^4.2.1",
-    "postcss": "^8.4.25",
+    "postcss": "^8.4.26",
     "prettier": "2.8.0",
     "react-test-renderer": "^18.2.0",
     "rimraf": "^5.0.1",