Remove searchEngine from App (#18540)

https://community-daily.mattermost.com/boards/workspace/zyoahc9uapdn3xdptac6jb69ic/285b80a3-257d-41f6-8cf4-ed80ca9d92e5/495cdb4d-c13a-4992-8eb9-80cfee2819a4?c=c6753a1c-dbbf-4316-8e4e-c58ebb65d6e0

```release-note
NONE
```

app/options.go

@@ -109,6 +109,5 @@ type AppOptionCreator func() []AppOption
 func ServerConnector(s *Server) AppOption {
 	return func(a *App) {
 		a.srv = s
-		a.searchEngine = s.SearchEngine
 	}
 }