Revert "api: add clear_all_relay_storage API"

This reverts commit 10ab556d65.

src/imap.rs

@@ -945,29 +945,6 @@ impl Session {
         Ok(())
     }
 
-    /// Deletes all messages from IMAP folder.
-    pub(crate) async fn delete_all_messages(
-        &mut self,
-        context: &Context,
-        folder: &str,
-    ) -> Result<()> {
-        let transport_id = self.transport_id();
-
-        if self.select_with_uidvalidity(context, folder).await? {
-            self.add_flag_finalized_with_set("1:*", "\\Deleted").await?;
-            self.selected_folder_needs_expunge = true;
-            context
-                .sql
-                .execute(
-                    "DELETE FROM imap WHERE transport_id=? AND folder=?",
-                    (transport_id, folder),
-                )
-                .await?;
-        }
-
-        Ok(())
-    }
-
     /// Moves batch of messages identified by their UID from the currently
     /// selected folder to the target folder.
     async fn move_message_batch(