Make ctrl-alt-b / cmd-alt-b toggle right dock (#33190)

Closes: https://github.com/zed-industries/zed/issues/33147

In VSCode ctrl-alt-b / cmd-alt-b toggles the right dock. Zed should
follow this behavior.

See also:
- https://github.com/zed-industries/zed/pull/31630

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -243,8 +243,7 @@
       "ctrl-alt-e": "agent::RemoveAllContext",
       "ctrl-shift-e": "project_panel::ToggleFocus",
       "ctrl-shift-enter": "agent::ContinueThread",
-      "alt-enter": "agent::ContinueWithBurnMode",
-      "ctrl-alt-b": "agent::ToggleBurnMode"
+      "alt-enter": "agent::ContinueWithBurnMode"
     }
   },
   {