build: bump postcss from 8.2.4 to 8.2.6 (#22032)

Bumps [postcss](https://github.com/postcss/postcss) from 8.2.4 to 8.2.6.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.2.4...8.2.6)

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

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

Author: dependabot[bot]

yarn.lock

@@ -10415,9 +10415,9 @@ postcss@^5.2.16:
     supports-color "^3.2.3"
 
 postcss@^8.1.7, postcss@^8.2.1:
-  version "8.2.4"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.2.4.tgz#20a98a39cf303d15129c2865a9ec37eda0031d04"
-  integrity sha512-kRFftRoExRVXZlwUuay9iC824qmXPcQQVzAjbCCgjpXnkdMCJYBu2gTwAaFBzv8ewND6O8xFb3aELmEkh9zTzg==
+  version "8.2.6"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.2.6.tgz#5d69a974543b45f87e464bc4c3e392a97d6be9fe"
+  integrity sha512-xpB8qYxgPuly166AGlpRjUdEYtmOWx2iCwGmrv4vqZL9YPVviDVPZPRXxnXr6xPZOdxQ9lp3ZBFCRgWJ7LE3Sg==
   dependencies:
     colorette "^1.2.1"
     nanoid "^3.1.20"