build(deps-dev): bump @typescript-eslint/eslint-plugin (#5596)

Bumps [@typescript-eslint/eslint-plugin](https://github.com/typescript-eslint/typescript-eslint/tree/HEAD/packages/eslint-plugin) from 6.20.0 to 6.21.0.
- [Release notes](https://github.com/typescript-eslint/typescript-eslint/releases)
- [Changelog](https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/CHANGELOG.md)
- [Commits](https://github.com/typescript-eslint/typescript-eslint/commits/v6.21.0/packages/eslint-plugin)

---
updated-dependencies:
- dependency-name: "@typescript-eslint/eslint-plugin"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

package-lock.json

@@ -14,7 +14,7 @@
     "@types/jquery": "3.5.29",
     "@types/mailparser": "3.4.4",
     "@types/node": "20.8.3",
-    "@typescript-eslint/eslint-plugin": "6.20.0",
+    "@typescript-eslint/eslint-plugin": "6.21.0",
     "@typescript-eslint/parser": "6.20.0",
     "ava": "5.3.1",
     "chai": "4.4.1",