build(deps): bump postcss from 8.4.30 to 8.4.31 in /demo

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.30 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@8.4.30...8.4.31)

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

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

demo/yarn.lock

@@ -208,9 +208,9 @@ picocolors@^1.0.0:
   integrity sha512-1fygroTLlHu66zi26VoTDv8yRgm0Fccecssto+MhsZ0D/DGW2sm8E8AjW7NU5VVTRt5GxbeZ5qBuJr+HyLYkjQ==
 
 postcss@^8.4.27:
-  version "8.4.30"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.30.tgz#0e0648d551a606ef2192a26da4cabafcc09c1aa7"
-  integrity sha512-7ZEao1g4kd68l97aWG/etQKPKq07us0ieSZ2TnFDk11i0ZfDW2AwKHYU8qv4MZKqN2fdBfg+7q0ES06UA73C1g==
+  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"