rename data provider file names

src/pages/repetition_settings.rs

@@ -1,7 +1,7 @@
 use crate::app::AppState;
 use crate::data::entities::DeckSettings;
-use crate::data_provider::card_sets::{delete_set, update_deck};
-use crate::data_provider::card_stats::{delete_stats, load_stats_of_deck};
+use crate::data_provider::decks::{delete_set, update_deck};
+use crate::data_provider::card_states::{delete_stats, load_stats_of_deck};
 use crate::navigation::Page::PreviousPage;
 use crate::navigation::{NavigatedPage, Page, RootMessage};
 use crate::notification::MaybeError;