Add more shortcuts for delete/restore in Git Panel (#27004)

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -752,6 +752,8 @@
       "escape": "git_panel::ToggleFocus",
       "ctrl-enter": "git::Commit",
       "alt-enter": "menu::SecondaryConfirm",
+      "delete": "git::RestoreFile",
+      "shift-delete": "git::RestoreFile",
       "backspace": "git::RestoreFile"
     }
   },

assets/keymaps/default-macos.json

@@ -791,6 +791,8 @@
       "shift-tab": "git_panel::FocusEditor",
       "escape": "git_panel::ToggleFocus",
       "cmd-enter": "git::Commit",
+      "delete": "git::RestoreFile",
+      "cmd-backspace": "git::RestoreFile",
       "backspace": "git::RestoreFile"
     }
   },