Bump react-i18next from 11.18.6 to 15.4.1 in /frontend/packages/core

Bumps [react-i18next](https://github.com/i18next/react-i18next) from 11.18.6 to 15.4.1.
- [Changelog](https://github.com/i18next/react-i18next/blob/master/CHANGELOG.md)
- [Commits](i18next/react-i18next@v11.18.6...v15.4.1)

---
updated-dependencies:
- dependency-name: react-i18next
  dependency-version: 15.4.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

frontend/packages/core/package.json

@@ -11,6 +11,6 @@
   "dependencies": {
     "i18next": "^21.3.2",
     "i18next-browser-languagedetector": "^6.0.0",
-    "react-i18next": "^11.0.0"
+    "react-i18next": "^15.4.1"
   }
 }