x11: fix fractional scaling when fract is 0.75

Fractional scaling was broken when the fractional part was .75 as
the round rounded up the WindowScalingFactor to the upper bound and
applied extra scaling in addition to the one in UnscaledDPI (1.75 *
2 for 175% scaling instead of 1.75 * 1)

src/xwayland.rs

@@ -692,7 +692,7 @@ impl Common {
                             ),
                             (
                                 "Gdk/WindowScalingFactor".into(),
-                                (new_scale.round() as i32).into(),
+                                (new_scale.floor() as i32).into(),
                             ),
                             (
                                 "Gtk/CursorThemeSize".into(),