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

crates/project_panel/src/project_panel_settings.rs

@@ -20,7 +20,6 @@ pub struct ProjectPanelSettings {
     pub git_status: bool,
     pub indent_size: f32,
     pub auto_reveal_entries: bool,
-    pub auto_fold_dirs: bool,
 }
 
 #[derive(Clone, Default, Serialize, Deserialize, JsonSchema, Debug)]
@@ -55,11 +54,6 @@ pub struct ProjectPanelSettingsContent {
     ///
     /// Default: true
     pub auto_reveal_entries: Option<bool>,
-    /// Whether to fold directories automatically
-    /// when directory has only one directory inside.
-    ///
-    /// Default: true
-    pub auto_fold_dirs: Option<bool>,
 }
 
 impl Settings for ProjectPanelSettings {