Fix window.layer.focusTraversalKeysEnabled = false (#114)

* Fix window.layer.focusTraversalKeysEnabled = false

Disabling focus keys didn't work

Test:
```
    window.layer.focusTraversalKeysEnabled = false
    window.layer.addKeyListener(object : KeyAdapter() {
        override fun keyPressed(event: KeyEvent) {
            println("keyPressed")
        }
    })
```

Press Tab or Shift-Tab. Before fix there was no output in console

* Remove unused import

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/SkiaLayer.kt

@@ -244,6 +244,10 @@ open class SkiaLayer(
         backedLayer.removeKeyListener(l)
     }
 
+    override fun setFocusTraversalKeysEnabled(focusTraversalKeysEnabled: Boolean) {
+        backedLayer.focusTraversalKeysEnabled = focusTraversalKeysEnabled
+    }
+
     /**
      * Redraw on the next animation Frame (on vsync signal if vsync is enabled).
      */