Fix for vim bindings in Pickers on Linux (#34840)

Closes: https://github.com/zed-industries/zed/issues/34780

Also relocated undo/redo selection in the keymap (no-op) as they are
from Sublime, not VSCode.

Release Notes:

- vim: Fixed an issue so `ctrl-w` / `ctrl-h` and `ctrl-u` work in
pickers on Linux when Vim mode is enabled.

assets/keymaps/vim.json

@@ -858,6 +858,14 @@
       "shift-n": null
     }
   },
+  {
+    "context": "Picker > Editor",
+    "bindings": {
+      "ctrl-h": "editor::Backspace",
+      "ctrl-u": "editor::DeleteToBeginningOfLine",
+      "ctrl-w": "editor::DeleteToPreviousWordStart"
+    }
+  },
   {
     "context": "GitCommit > Editor && VimControl && vim_mode == normal",
     "bindings": {