chore(deps): bump vue-i18n from 8.14.1 to 8.15.0 in /frontend (#881)

Bumps [vue-i18n](https://github.com/kazupon/vue-i18n) from 8.14.1 to 8.15.0.
- [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/v8.14.1...v8.15.0)

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

frontend/package-lock.json

@@ -12364,9 +12364,9 @@
       "dev": true
     },
     "vue-i18n": {
-      "version": "8.14.1",
-      "resolved": "https://registry.npmjs.org/vue-i18n/-/vue-i18n-8.14.1.tgz",
-      "integrity": "sha512-uHzw5GTFyf/TmjJXveSl3L4CG61KI4lvhKOQvx8W4Y8P2LZ3v3l/qw4KRs1C6pWyjkfY9p0rezYNFO5YzMEQ8A=="
+      "version": "8.15.0",
+      "resolved": "https://registry.npmjs.org/vue-i18n/-/vue-i18n-8.15.0.tgz",
+      "integrity": "sha512-juJ/avAP39bOMycC+qQDLJ8U9z9LtLF/9PsRoJLBSfsYZo9bqYntyyX5QPicwlb1emJKjgxhZ3YofHiQcXBu0Q=="
     },
     "vue-loader": {
       "version": "15.7.1",

frontend/package.json

@@ -19,7 +19,7 @@
     "noty": "^3.2.0-beta",
     "qrcode.vue": "^1.6.3",
     "vue": "^2.6.10",
-    "vue-i18n": "^8.14.1",
+    "vue-i18n": "^8.15.0",
     "vue-router": "^3.1.3",
     "vuex": "^3.1.1",
     "vuex-router-sync": "^5.0.0"