Move keyboard shortcut for pane::GoForward (#38221)

Move keyboard shortcut for `pane:GoForward` so it's going to be
displayed as a shortcut hint in UI. Currently `Forward` is shown as a
hint, which isn't consistent with `GoBack` action and can be confusing.

Release Notes: 

- Improved the displayed keybinding for the `pane::GoForward` action on
Linux.

assets/keymaps/default-linux.json

@@ -462,8 +462,8 @@
       "ctrl-k ctrl-w": "workspace::CloseAllItemsAndPanes",
       "back": "pane::GoBack",
       "ctrl-alt--": "pane::GoBack",
-      "ctrl-alt-_": "pane::GoForward",
       "forward": "pane::GoForward",
+      "ctrl-alt-_": "pane::GoForward",
       "ctrl-alt-g": "search::SelectNextMatch",
       "f3": "search::SelectNextMatch",
       "ctrl-alt-shift-g": "search::SelectPreviousMatch",