⬆️ Bump firebase from 7.15.3 to 7.15.4

Bumps [firebase](https://github.com/firebase/firebase-js-sdk) from 7.15.3 to 7.15.4.
- [Release notes](https://github.com/firebase/firebase-js-sdk/releases)
- [Commits](https://github.com/firebase/firebase-js-sdk/compare/firebase@7.15.3...firebase@7.15.4)

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

package.json

@@ -36,7 +36,7 @@
     "@nuxtjs/sitemap": "^2.3.2",
     "@nuxtjs/toast": "^3.3.0",
     "ace-builds": "^1.4.11",
-    "firebase": "^7.15.3",
+    "firebase": "^7.15.4",
     "graphql": "^15.1.0",
     "graphql-language-service-interface": "^2.4.0",
     "nuxt": "^2.12.2",