gf keybinding open the selected explorer file in the previous tab

[richardgill]

keymaps.view.open_in_prev_tab (gf) is currently a no-op when the explorer pane has focus.

Reproduce

1. :CodeDiff
2. Focus explorer
3. Select a file
4. Press gf

Expected

Open the selected explorer file in the previous tab (or create one).

AI generated fix PR (feel free to discard): #321