Bump vue-i18n from 8.26.2 to 8.26.4 in /frontend

Bumps [vue-i18n](https://github.com/kazupon/vue-i18n) from 8.26.2 to 8.26.4.
- [Release notes](https://github.com/kazupon/vue-i18n/releases)
- [Changelog](https://github.com/kazupon/vue-i18n/blob/v8.x/CHANGELOG.md)
- [Commits](https://github.com/kazupon/vue-i18n/compare/v8.26.2...v8.26.4)

---
updated-dependencies:
- dependency-name: vue-i18n
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

frontend/package.json

@@ -14,7 +14,7 @@
     "socket.io-client": "^4.2.0",
     "vue": "^2.6.14",
     "vue-clipboard2": "^0.3.3",
-    "vue-i18n": "^8.26.2",
+    "vue-i18n": "^8.26.4",
     "vue-router": "^3.5.2",
     "vue-socket.io": "^3.0.10"
   },

frontend/yarn.lock

@@ -8774,10 +8774,10 @@ vue-hot-reload-api@^2.3.0:
   resolved "https://registry.npm.taobao.org/vue-hot-reload-api/download/vue-hot-reload-api-2.3.4.tgz#532955cc1eb208a3d990b3a9f9a70574657e08f2"
   integrity sha1-UylVzB6yCKPZkLOp+acFdGV+CPI=
 
-vue-i18n@^8.26.2:
-  version "8.26.2"
-  resolved "https://registry.yarnpkg.com/vue-i18n/-/vue-i18n-8.26.2.tgz#86a1ab9330bae7a56f58f23a52355f68aad00222"
-  integrity sha512-koaC7gEYcedlzq9M8usTbD/v3DdLZ8suvwuanrs6aBIiM/sVqq2nQPbeuNPrpHaXgpR/pff2+/R+lFGKl7S1cQ==
+vue-i18n@^8.26.4:
+  version "8.26.4"
+  resolved "https://registry.yarnpkg.com/vue-i18n/-/vue-i18n-8.26.4.tgz#c6d40cf083a84f20cb2b55dc3f4e07806fcfadf5"
+  integrity sha512-ngwndlGMXBNtq3tjsIVzNW/yT7+iUgbUuBimH/1OAomy5UezzfKDzunDexLkVoeN3DeckWnsE+cZwK83cx0JMA==
 
 "vue-loader-v16@npm:vue-loader@^16.1.0":
   version "16.2.0"