emacs: Fix ctrl-p/ctrl-n navigating popover menus (#33218)

Closes https://github.com/zed-industries/zed/issues/33200

Release Notes:

- emacs: Fixed ctrl-p/ctrl-n keyboard navigation of autocomplete/code
actions menus

assets/keymaps/linux/emacs.json

@@ -90,6 +90,13 @@
       "ctrl-g": "editor::Cancel"
     }
   },
+  {
+    "context": "Editor && (showing_code_actions || showing_completions)",
+    "bindings": {
+      "ctrl-p": "editor::ContextMenuPrevious",
+      "ctrl-n": "editor::ContextMenuNext"
+    }
+  },
   {
     "context": "Workspace",
     "bindings": {