Bump elm/core from 1.0.2 to 1.0.4 in /frontend

Bumps [elm/core](https://github.com/elm/core) from 1.0.2 to 1.0.4.
- [Release notes](https://github.com/elm/core/releases)
- [Changelog](https://github.com/elm/core/blob/master/changelog.md)
- [Commits](https://github.com/elm/core/compare/1.0.2...1.0.4)

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

frontend/elm.json

@@ -7,7 +7,7 @@
     "dependencies": {
         "direct": {
             "elm/browser": "1.0.1",
-            "elm/core": "1.0.2",
+            "elm/core": "1.0.4",
             "elm/html": "1.0.0",
             "elm/svg": "1.0.1",
             "elm-community/maybe-extra": "5.0.0"