chore(deps): bump postcss from 8.5.6 to 8.5.12 in /web-frontend (baserow#5273)

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.6 to 8.5.12.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.6...8.5.12)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.12
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

web-frontend/yarn.lock

@@ -10643,19 +10643,10 @@ postcss-value-parser@^4.2.0:
   resolved "https://registry.yarnpkg.com/postcss-value-parser/-/postcss-value-parser-4.2.0.tgz#723c09920836ba6d3e5af019f92bc0971c02e514"
   integrity sha512-1NNCs6uurfkVbeXG4S8JFT9t19m45ICnif8zWLd5oPSZ50QnwMfK+H3jv408d4jw/7Bttv5axS5IiHoLaVNHeQ==
 
-postcss@^8.4.24:
-  version "8.5.6"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.5.6.tgz#2825006615a619b4f62a9e7426cc120b349a8f3c"
-  integrity sha512-3Ybi1tAuwAP9s0r1UQ2J4n5Y0G05bJkpUIO0/bI9MhwmD70S5aTWbXGBwxHrelT+XM1k6dM0pk+SwNkpTRN7Pg==
-  dependencies:
-    nanoid "^3.3.11"
-    picocolors "^1.1.1"
-    source-map-js "^1.2.1"
-
-postcss@^8.5.6, postcss@^8.5.8:
-  version "8.5.8"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.5.8.tgz#6230ecc8fb02e7a0f6982e53990937857e13f399"
-  integrity sha512-OW/rX8O/jXnm82Ey1k44pObPtdblfiuWnrd8X7GJ7emImCOstunGbXUpp7HdBrFQX6rJzn3sPT397Wp5aCwCHg==
+postcss@^8.4.24, postcss@^8.5.6, postcss@^8.5.8:
+  version "8.5.12"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.5.12.tgz#cd0c0f667f7cb0521e2313234ea6e707a9ec1ddb"
+  integrity sha512-W62t/Se6rA0Az3DfCL0AqJwXuKwBeYg6nOaIgzP+xZ7N5BFCI7DYi1qs6ygUYT6rvfi6t9k65UMLJC+PHZpDAA==
   dependencies:
     nanoid "^3.3.11"
     picocolors "^1.1.1"