[sway/workspaces] window-rewrite only works if undocumented option window-format is set

[prTopi]

From what I can tell window-format is a removed earlier version of window-rewrite that isn't used anywhere anymore.
There however is still a check for if that config option is set to any string, that prevents the windows format from updating if it isn't passed.

The check for window-format happens on line 333 in sway/workspaces.cpp