Bump nth-check and unist-util-select in /tools/doc (#8652)

Bumps [nth-check](https://github.com/fb55/nth-check) to 2.1.1 and updates ancestor dependency [unist-util-select](https://github.com/syntax-tree/unist-util-select). These dependencies need to be updated together.


Updates `nth-check` from 1.0.2 to 2.1.1
- [Release notes](https://github.com/fb55/nth-check/releases)
- [Commits](https://github.com/fb55/nth-check/compare/v1.0.2...v2.1.1)

Updates `unist-util-select` from 2.0.0 to 4.0.3
- [Release notes](https://github.com/syntax-tree/unist-util-select/releases)
- [Commits](https://github.com/syntax-tree/unist-util-select/compare/2.0.0...4.0.3)

---
updated-dependencies:
- dependency-name: nth-check
  dependency-type: indirect
- dependency-name: unist-util-select
  dependency-type: direct:production
...

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

tools/doc/package.json

@@ -23,7 +23,7 @@
     "rxjs": "^6.6.6",
     "typedoc": "^0.24.8",
     "typescript": "3.9.8",
-    "unist-util-select": "2.0.0"
+    "unist-util-select": "4.0.3"
   },
   "devDependencies": {
     "@paperist/types-remark": "0.1.3",