feat: Revert "Don't fetch messages from unknown folders (#7190)"

This reverts commit 2260156c40. Some users still want to get messages
from all folders as reported by @gerryfrancis.

src/imap.rs

@@ -823,10 +823,7 @@ impl Session {
             .context("listing folders for resync")?;
         for folder in all_folders {
             let folder_meaning = get_folder_meaning(&folder);
-            if !matches!(
-                folder_meaning,
-                FolderMeaning::Virtual | FolderMeaning::Unknown
-            ) {
+            if folder_meaning != FolderMeaning::Virtual {
                 self.resync_folder_uids(context, folder.name(), folder_meaning)
                     .await?;
             }

src/imap/scan_folders.rs

@@ -74,7 +74,6 @@ impl Imap {
             // Don't scan folders that are watched anyway
             if !watched_folders.contains(&folder.name().to_string())
                 && folder_meaning != FolderMeaning::Trash
-                && folder_meaning != FolderMeaning::Unknown
             {
                 self.fetch_move_delete(context, session, folder.name(), folder_meaning)
                     .await