Inject a StringProvider instead of the context, and update tests.

Also remove the other StringProvider we had, it was not used anymore

services/apperror/api/src/main/kotlin/io/element/android/services/apperror/api/AppErrorStateService.kt

@@ -16,5 +16,4 @@ interface AppErrorStateService {
     fun showError(title: String, body: String)
 
     fun showError(@StringRes titleRes: Int, @StringRes bodyRes: Int)
-
 }