Revert "Add setting to show/hide title bar (#37428)" (#38756)

Closes https://github.com/zed-industries/zed/issues/38547

Release Notes:

- Reverted the ability to show/hide the titlebar. This caused rendering
bugs on
macOS, and we're preparing for the redesign which requires the toolbar
being present.

---------

Co-authored-by: Kirill Bulatov <kirill@zed.dev>

assets/settings/default.json

@@ -391,8 +391,6 @@
   "use_system_window_tabs": false,
   // Titlebar related settings
   "title_bar": {
-    // When to show the title bar: "always" | "never" | "hide_in_full_screen".
-    "show": "always",
     // Whether to show the branch icon beside branch switcher in the titlebar.
     "show_branch_icon": false,
     // Whether to show the branch name button in the titlebar.