Bump clean-css from 4.2.1 to 4.2.3 (#579)

Bumps [clean-css](https://github.com/jakubpawlowicz/clean-css) from 4.2.1 to 4.2.3.
- [Release notes](https://github.com/jakubpawlowicz/clean-css/releases)
- [Changelog](https://github.com/jakubpawlowicz/clean-css/blob/v4.2.3/History.md)
- [Commits](https://github.com/jakubpawlowicz/clean-css/compare/v4.2.1...v4.2.3)

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

package-lock.json

@@ -962,9 +962,9 @@
       }
     },
     "clean-css": {
-      "version": "4.2.1",
-      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-4.2.1.tgz",
-      "integrity": "sha512-4ZxI6dy4lrY6FHzfiy1aEOXgu4LIsW2MhwG0VBKdcoGoH/XLFgaHSdLTGr4O8Be6A8r3MOphEiI8Gc1n0ecf3g==",
+      "version": "4.2.3",
+      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-4.2.3.tgz",
+      "integrity": "sha512-VcMWDN54ZN/DS+g58HYL5/n4Zrqe8vHJpGA8KdgUXFU4fuP/aHNw8eld9SyEIyabIMJX/0RaY/fplOo5hYLSFA==",
       "dev": true,
       "requires": {
         "source-map": "~0.6.0"

package.json

@@ -41,7 +41,7 @@
     "@11ty/eleventy": "^0.11.0",
     "@11ty/eleventy-plugin-syntaxhighlight": "^2.0.3",
     "all-contributors-cli": "^6.8.1",
-    "clean-css": "^4.2.1",
+    "clean-css": "^4.2.3",
     "html-minifier": "^4.0.0",
     "luxon": "^1.17.2",
     "markdown-it": "^9.0.1",