Bump cssnano from 5.1.15 to 6.0.0 (#12629)

Bumps [cssnano](https://github.com/cssnano/cssnano) from 5.1.15 to 6.0.0.
- [Release notes](https://github.com/cssnano/cssnano/releases)
- [Commits](https://github.com/cssnano/cssnano/compare/cssnano@5.1.15...cssnano@6.0.0)

---
updated-dependencies:
- dependency-name: cssnano
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

package.json

@@ -49,7 +49,7 @@
     "chalk": "^5.0.1",
     "chokidar": "^3.5.3",
     "cross-env": "^7.0.3",
-    "cssnano": "^5.1.13",
+    "cssnano": "^6.0.0",
     "d3": "^7.6.1",
     "d3-queue": "^3.0.7",
     "diff": "^5.1.0",