Re-enable window decorations

[hannobraun]

Window decorations are currently disabled, as per this comment:

fornjot/crates/fj-window/src/window.rs

Lines 13 to 32 in d74949b

	// When the window decorations are enabled, I'm seeing the following
	// error on Gnome/Wayland, in response to a `ScaleFactorChange`
	// event:
	// ```
	// wl_surface@24: error 2: Buffer size (1940x45) must be an integer multiple of the buffer_scale (2).
	// ```
	//
	// This is happening most of the time. Very rarely, the window will
	// open as expected.
	//
	// I believe that there is a race condition somewhere low in the
	// stack, that will cause the buffer size for the window decorations
	// to not be updated before the check that produces the above error.
	// I failed to track down where this is happening, so I decided to
	// deploy this workaround instead of spending more time.
	//
	// Window decorations should be re-enabled once possible. This is
	// being tracked in this issue:
	// https://github.com/hannobraun/fornjot/issues/1848
	.with_decorations(false)

Once whatever bug that caused this error has been fixed, window decorations should be enabled again.