fix: no window border on new mpv windows versions

There's a lot of `title-bar` interaction weirdness on windows. When disabling it on newer mpv versions, one version hides borders, other doesn't. So let's just pretend this setting does what it's supposed to and what everyone would expect, and only hides the title bar without touching the border. People can always disable uosc's window border with other options if they need to.

src/uosc/elements/WindowBorder.lua

@@ -12,7 +12,6 @@ end
 
 function WindowBorder:decide_enabled()
 	self.enabled = options.window_border_size > 0 and not state.fullormaxed and not state.border
-		and (state.platform ~= 'windows' or state.title_bar ~= true)
 	self.size = self.enabled and round(options.window_border_size * state.scale) or 0
 end