chore(deps): bump vue-i18n from 8.15.1 to 8.15.3 in /frontend

Bumps [vue-i18n](https://github.com/kazupon/vue-i18n) from 8.15.1 to 8.15.3.
- [Release notes](https://github.com/kazupon/vue-i18n/releases)
- [Changelog](https://github.com/kazupon/vue-i18n/blob/dev/CHANGELOG.md)
- [Commits](https://github.com/kazupon/vue-i18n/compare/v8.15.1...v8.15.3)

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

frontend/package.json

@@ -19,7 +19,7 @@
     "noty": "^3.2.0-beta",
     "qrcode.vue": "^1.7.0",
     "vue": "^2.6.10",
-    "vue-i18n": "^8.15.1",
+    "vue-i18n": "^8.15.3",
     "vue-router": "^3.1.3",
     "vuex": "^3.1.2",
     "vuex-router-sync": "^5.0.0"