remove the *mode*-specific bindings, e.g. <c-k> in *emacs*

this commit also adds the `help_menu` binding on `<c-h>`

crates/nu-utils/src/sample_config/default_config.nu

@@ -365,93 +365,19 @@ $env.config = {
         ]
       }
     }
-    {
-      name: completion_previous
-      modifier: shift
-      keycode: backtab
-      mode: [emacs, vi_normal, vi_insert] # Note: You can add the same keybinding to all modes by using a list
-      event: { send: menuprevious }
-    }
     {
       name: history_menu
       modifier: control
       keycode: char_r
-      mode: emacs
+      mode: [emacs, vi_insert, vi_normal]
       event: { send: menu name: history_menu }
     }
     {
-      name: next_page
+      name: help_menu
       modifier: control
-      keycode: char_x
+      keycode: char_h
-      mode: emacs
+      mode: [emacs, vi_insert, vi_normal]
-      event: { send: menupagenext }
+      event: { send: menu name: help_menu }
-    }
-    {
-      name: undo_or_previous_page
-      modifier: control
-      keycode: char_z
-      mode: emacs
-      event: {
-        until: [
-          { send: menupageprevious }
-          { edit: undo }
-        ]
-       }
-    }
-    {
-      name: yank
-      modifier: control
-      keycode: char_y
-      mode: emacs
-      event: {
-        until: [
-          {edit: pastecutbufferafter}
-        ]
-      }
-    }
-    {
-      name: unix-line-discard
-      modifier: control
-      keycode: char_u
-      mode: [emacs, vi_normal, vi_insert]
-      event: {
-        until: [
-          {edit: cutfromlinestart}
-        ]
-      }
-    }
-    {
-      name: kill-line
-      modifier: control
-      keycode: char_k
-      mode: [emacs, vi_normal, vi_insert]
-      event: {
-        until: [
-          {edit: cuttolineend}
-        ]
-      }
-    }
-    # Keybindings used to trigger the user defined menus
-    {
-      name: commands_menu
-      modifier: control
-      keycode: char_t
-      mode: [emacs, vi_normal, vi_insert]
-      event: { send: menu name: commands_menu }
-    }
-    {
-      name: vars_menu
-      modifier: alt
-      keycode: char_o
-      mode: [emacs, vi_normal, vi_insert]
-      event: { send: menu name: vars_menu }
-    }
-    {
-      name: commands_with_description
-      modifier: control
-      keycode: char_s
-      mode: [emacs, vi_normal, vi_insert]
-      event: { send: menu name: commands_with_description }
     }
   ]
 }