build(deps): bump vega-expression and vega-lite in /docs

Bumps [vega-expression](https://github.com/vega/vega) to 5.2.1 and updates ancestor dependency [vega-lite](https://github.com/vega/vega-lite). These dependencies need to be updated together.


Updates `vega-expression` from 5.2.0 to 5.2.1
- [Release notes](https://github.com/vega/vega/releases)
- [Commits](https://github.com/vega/vega/commits)

Updates `vega-lite` from 5.23.0 to 6.4.1
- [Release notes](https://github.com/vega/vega-lite/releases)
- [Changelog](https://github.com/vega/vega-lite/blob/main/CHANGELOG.md)
- [Commits](vega/vega-lite@v5.23.0...v6.4.1)

---
updated-dependencies:
- dependency-name: vega-expression
  dependency-version: 5.2.1
  dependency-type: indirect
- dependency-name: vega-lite
  dependency-version: 6.4.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

docs/package-lock.json

@@ -13,7 +13,7 @@
   "dependencies": {
     "preact": "^10.26.5",
     "vega": "^5.30.0",
-    "vega-lite": "^5.21.0"
+    "vega-lite": "^6.4.1"
   },
   "devDependencies": {
     "@eslint/js": "^9.25.1",