build(deps): bump postcss from 8.4.21 to 8.4.31 in /website

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.21 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.21...8.4.31)

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

Signed-off-by: dependabot[bot] <[email protected]>

website/yarn.lock

@@ -8514,11 +8514,6 @@ [email protected], mute-stream@~0.0.4:
   resolved "https://registry.yarnpkg.com/mute-stream/-/mute-stream-0.0.8.tgz#1630c42b2251ff81e2a283de96a5497ea92e5e0d"
   integrity sha512-nnbWWOkoWyUsTjKrhgD0dcz22mdkSnpYqbEjIm2nhwhuxlSkpywJmBo8h0ZqJdkp73mb90SssHkN4rsRaBAfAA==
 
-nanoid@^3.3.4:
-  version "3.3.4"
-  resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.4.tgz#730b67e3cd09e2deacf03c027c81c9d9dbc5e8ab"
-  integrity sha512-MqBkQh/OHTS2egovRtLk45wEyNXwF+cokD+1YPf9u5VfJiRdAiRwB2froX5Co9Rh20xs4siNPm8naNotSD6RBw==
-
 nanoid@^3.3.6:
   version "3.3.6"
   resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.6.tgz#443380c856d6e9f9824267d960b4236ad583ea4c"
@@ -9448,19 +9443,10 @@ postcss-value-parser@^4.0.2, postcss-value-parser@^4.1.0, postcss-value-parser@^
   resolved "https://registry.yarnpkg.com/postcss-value-parser/-/postcss-value-parser-4.2.0.tgz#723c09920836ba6d3e5af019f92bc0971c02e514"
   integrity sha512-1NNCs6uurfkVbeXG4S8JFT9t19m45ICnif8zWLd5oPSZ50QnwMfK+H3jv408d4jw/7Bttv5axS5IiHoLaVNHeQ==
 
-postcss@^8.2.15, postcss@^8.2.9, postcss@^8.3.11:
-  version "8.4.21"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.21.tgz#c639b719a57efc3187b13a1d765675485f4134f4"
-  integrity sha512-tP7u/Sn/dVxK2NnruI4H9BG+x+Wxz6oeZ1cJ8P6G/PZY0IKk4k/63TDsQf2kQq3+qoJeLm2kIBUNlZe3zgb4Zg==
-  dependencies:
-    nanoid "^3.3.4"
-    picocolors "^1.0.0"
-    source-map-js "^1.0.2"
-
-postcss@^8.4.24:
-  version "8.4.30"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.30.tgz#0e0648d551a606ef2192a26da4cabafcc09c1aa7"
-  integrity sha512-7ZEao1g4kd68l97aWG/etQKPKq07us0ieSZ2TnFDk11i0ZfDW2AwKHYU8qv4MZKqN2fdBfg+7q0ES06UA73C1g==
+postcss@^8.2.15, postcss@^8.2.9, postcss@^8.3.11, postcss@^8.4.24:
+  version "8.4.31"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.31.tgz#92b451050a9f914da6755af352bdc0192508656d"
+  integrity sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==
   dependencies:
     nanoid "^3.3.6"
     picocolors "^1.0.0"