chores(rust): Remove unused functions

src/backend/message/display_message.rs

@@ -51,13 +51,6 @@ impl DisplayMessage {
 
 pub trait DisplayMessageExt: 'static {
     fn textual_description(&self) -> Option<String>;
-
-    fn send_notification(&self)
-    where
-        Self: IsA<DisplayMessage>,
-    {
-        self.upcast_ref::<DisplayMessage>().send_notification()
-    }
 }
 
 impl<O: IsA<DisplayMessage>> DisplayMessageExt for O {

src/backend/timeline/timeline_item.rs

@@ -12,10 +12,6 @@ pub trait TimelineItemExt: 'static + std::marker::Sized + glib::prelude::ObjectE
     /// Set if this item should show the timestamp based on the next item.
     fn update_show_timestamp(&self, next: Option<&TimelineItem>);
 
-    fn datetime(&self) -> Option<glib::DateTime> {
-        self.property("datetime")
-    }
-
     /// Days since 01.01.1970
     fn day_timestamp(&self) -> u64 {
         self.timestamp() / (1000 * 60 * 60 * 24)
@@ -26,10 +22,6 @@ pub trait TimelineItemExt: 'static + std::marker::Sized + glib::prelude::ObjectE
         self.property("timestamp")
     }
 
-    fn set_timestamp(&self, value: u64) {
-        self.set_property("timestamp", value)
-    }
-
     fn show_header(&self) -> bool {
         self.property("show-header")
     }