fix: app/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-VUEI18N-10771082

Author: snyk-bot

app/package.json

@@ -37,7 +37,7 @@
     "buefy": "^0.9.8",
     "dotenv-webpack": "^2.0.0",
     "vue": "^2.6.11",
-    "vue-i18n": "^8.25.0",
+    "vue-i18n": "^9.14.5",
     "vue-meta": "^2.3.3",
     "vue-router": "^3.5.2",
     "vuex": "^3.1.2"