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/default-linux.json

@@ -484,8 +484,6 @@
       "ctrl-k ctrl-shift-d": ["editor::SelectPrevious", { "replace_newest": true }], // editor.action.moveSelectionToPreviousFindMatch
       "ctrl-k ctrl-i": "editor::Hover",
       "ctrl-/": ["editor::ToggleComments", { "advance_downwards": false }],
-      "ctrl-u": "editor::UndoSelection",
-      "ctrl-shift-u": "editor::RedoSelection",
       "f8": ["editor::GoToDiagnostic", { "severity": { "min": "hint", "max": "error" } }],
       "shift-f8": ["editor::GoToPreviousDiagnostic", { "severity": { "min": "hint", "max": "error" } }],
       "f2": "editor::Rename",
@@ -663,6 +661,8 @@
   {
     "context": "Editor",
     "bindings": {
+      "ctrl-u": "editor::UndoSelection",
+      "ctrl-shift-u": "editor::RedoSelection",
       "ctrl-shift-j": "editor::JoinLines",
       "ctrl-alt-backspace": "editor::DeleteToPreviousSubwordStart",
       "ctrl-alt-h": "editor::DeleteToPreviousSubwordStart",