keyboard: Fix setting height in portrait orientation

get_preferred_height() returns both the minimum and natural height,
not a single size. Math.min() doesn't handle that and returns NaN,
whoops.

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2349

js/ui/keyboard.js

@@ -1608,7 +1608,8 @@ class Keyboard extends St.BoxLayout {
              * we allow the OSK being smaller than 1/3rd of the monitor height
              * there.
              */
-            this.height = Math.min(maxHeight, this.get_preferred_height(monitor.width));
+            const [, natHeight] = this.get_preferred_height(monitor.width);
+            this.height = Math.min(maxHeight, natHeight);
         }
     }