Apparently <c-h> sends <BS> to xterm256-screen terminals and your binding doesn’t work in Neovim.

There’s a few fixes, but I like this one that does it in iTerm:

1. Edit -> Preferences -> Keys
2. Press +
3. Press Ctrl+h as Keyboard Shortcut
4. Choose Send Escape Sequence as Action
5. Type [104;5u for Esc+