Bump eslint from 9.29.0 to 9.31.0 in /webapp (#4474)

Bumps [eslint](https://github.com/eslint/eslint) from 9.29.0 to 9.31.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/main/CHANGELOG.md)
- [Commits](eslint/eslint@v9.29.0...v9.31.0)

---
updated-dependencies:
- dependency-name: eslint
  dependency-version: 9.31.0
  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]

webapp/package-lock.json

@@ -34,7 +34,7 @@
     "@eslint/js": "^9.29.0",
     "@polymer/test-fixture": "4.0.2",
     "cpy-cli": "5.0.0",
-    "eslint": "9.29.0",
+    "eslint": "9.31.0",
     "eslint-plugin-html": "8.1.3",
     "globals": "^16.3.0",
     "wct-browser-legacy": "1.0.2",