fix: remove duplicate kitty backspace keybinds

[hougesen]

The deleted keybindings were duplicates of

rio/frontends/cross-winit/src/screen/bindings/mod.rs

Lines 742 to 744 in 208e913

	Key::Named(Backspace), ~BindingMode::VI, ~BindingMode::ALL_KEYS_AS_ESC; Action::Esc("\x7f".into());
	Key::Named(Backspace), ModifiersState::ALT, ~BindingMode::VI, ~BindingMode::ALL_KEYS_AS_ESC; Action::Esc("\x1b\x7f".into());
	Key::Named(Backspace), ModifiersState::SHIFT, ~BindingMode::VI, ~BindingMode::ALL_KEYS_AS_ESC; Action::Esc("\x7f".into());

with the only difference between them being the spaces.

After deleting the lines I no longer had any issues with backspace deleting 2 characters when Kitty protocol is turned on (#344).

Before with Kitty false:

Before with Kitty true:

After with Kitty false:

After with Kitty true:

[raphamorim]

Good finding! I forgot to remove it when porting kitty keyboard to config.
Tested and looks good 👌