Revert "macOS: Improve deadkeys (#20515)" (#20570)

This reverts commit https://github.com/zed-industries/zed/pull/20515

I'm reverting for now to fix issues with key bindings on Nightly:
* `ctrl-c` and `ctrl-m` are being treated as `ctrl-enter`
* `ctrl-[` isn't working in vim mode
* there's a delay before `cmd-shift-[` switches tabs w/ vim mode enabled

Release Notes:

- N/A

crates/terminal_view/src/terminal_element.rs

@@ -1044,10 +1044,6 @@ impl InputHandler for TerminalInputHandler {
     ) -> Option<Bounds<Pixels>> {
         self.cursor_bounds
     }
-
-    fn apple_press_and_hold_enabled(&mut self) -> bool {
-        false
-    }
 }
 
 pub fn is_blank(cell: &IndexedCell) -> bool {