build(deps): bump postcss from 8.2.14 to 8.2.15 (#3870)

Bumps [postcss](https://github.com/postcss/postcss) from 8.2.14 to 8.2.15.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.2.14...8.2.15)

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

Author: dependabot[bot]

package-lock.json

@@ -57,7 +57,7 @@
     "ncp": "^2.0.0",
     "node-version-data": "^1.1.0",
     "npm-run-all": "^4.1.5",
-    "postcss": "^8.2.14",
+    "postcss": "^8.2.15",
     "sass": "^1.32.12",
     "semver": "^7.3.5",
     "strftime": "^0.10.0"