build(deps): bump i18next from 23.13.0 to 23.15.1 in /frontend

Bumps [i18next](https://github.com/i18next/i18next) from 23.13.0 to 23.15.1.
- [Release notes](https://github.com/i18next/i18next/releases)
- [Changelog](https://github.com/i18next/i18next/blob/master/CHANGELOG.md)
- [Commits](i18next/i18next@v23.13.0...v23.15.1)

---
updated-dependencies:
- dependency-name: i18next
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

frontend/package.json

@@ -31,7 +31,7 @@
     "date-fns": "3.6.0",
     "formik": "2.4.6",
     "formik-wizard-form": "2.1.0",
-    "i18next": "23.13.0",
+    "i18next": "23.15.1",
     "lodash": "4.17.21",
     "markdown-to-jsx": "7.4.7",
     "next": "14.2.5",