build(deps): bump postcss in /src/packages/excalidraw

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.8 to 8.4.31.
- [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/8.4.8...8.4.31)

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

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

src/packages/excalidraw/yarn.lock

@@ -3293,11 +3293,6 @@ multicast-dns@^7.2.4:
     dns-packet "^5.2.2"
     thunky "^1.0.2"
 
-nanoid@^3.3.1:
-  version "3.3.1"
-  resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.1.tgz#6347a18cac88af88f58af0b3594b723d5e99bb35"
-  integrity sha512-n6Vs/3KGyxPQd6uO0eH4Bv0ojGSUvuLlIHtC3Y0kEO23YRge8H9x1GCzLn28YX0H66pMkxuaeESFq4tKISKwdw==
-
 nanoid@^3.3.2, nanoid@^3.3.6:
   version "3.3.6"
   resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.6.tgz#443380c856d6e9f9824267d960b4236ad583ea4c"
@@ -3583,11 +3578,11 @@ postcss-value-parser@^4.1.0, postcss-value-parser@^4.2.0:
   integrity sha512-1NNCs6uurfkVbeXG4S8JFT9t19m45ICnif8zWLd5oPSZ50QnwMfK+H3jv408d4jw/7Bttv5axS5IiHoLaVNHeQ==
 
 postcss@^8.4.7:
-  version "8.4.8"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.8.tgz#dad963a76e82c081a0657d3a2f3602ce10c2e032"
-  integrity sha512-2tXEqGxrjvAO6U+CJzDL2Fk2kPHTv1jQsYkSoMeOis2SsYaXRO2COxTdQp99cYvif9JTXaAk9lYGc3VhJt7JPQ==
+  version "8.4.31"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.31.tgz#92b451050a9f914da6755af352bdc0192508656d"
+  integrity sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==
   dependencies:
-    nanoid "^3.3.1"
+    nanoid "^3.3.6"
     picocolors "^1.0.0"
     source-map-js "^1.0.2"