build(deps): bump postcss from 7.0.21 to 7.0.23 (#2786)

Bumps [postcss](https://github.com/postcss/postcss) from 7.0.21 to 7.0.23.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/master/CHANGELOG.md)
- [Commits](postcss/postcss@7.0.21...7.0.23)

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

Author: dependabot-preview[bot]

package-lock.json

@@ -61,7 +61,7 @@
     "node-version-data": "^1.1.0",
     "npm-run-all": "^4.1.5",
     "octonode": "^0.9.5",
-    "postcss": "^7.0.21",
+    "postcss": "^7.0.23",
     "request": "^2.88.0",
     "semver": "^6.3.0",
     "strftime": "^0.10.0"