Revert "Add support of auto folded directories" (#8476)

Reverts zed-industries/zed#7674

@ABckh: reverting this as it introduced a significant performance
slowdown, most likely caused by iterating through all the snapshot
entries to determine whether a directory is foldable/unfoldable/omitted.
It would be great if you could open a new PR that reverts this revert
and addresses the performance issues. Thank you!

/cc: @maxbrunsfeld 

Release notes:

- N/A

assets/settings/default.json

@@ -193,10 +193,7 @@
     // Whether to reveal it in the project panel automatically,
     // when a corresponding project entry becomes active.
     // Gitignored entries are never auto revealed.
-    "auto_reveal_entries": true,
-    /// Whether to fold directories automatically
-    /// when directory has only one directory inside.
-    "auto_fold_dirs": true
+    "auto_reveal_entries": true
   },
   "collaboration_panel": {
     // Whether to show the collaboration panel button in the status bar.