[gnome-shell] keyboard: Add missing setter

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 3ba4304da9077552c95e5a96d2bbdca5dd7088da
Author: Florian Müllner <fmuellner gnome org>
Date:   Mon Apr 27 23:45:21 2020 +0200

    keyboard: Add missing setter
    
    We override the :visible property for the keyboard actor, but don't
    provide a corresponding setter. The property is therefore read-only
    on the javascript level, and any attempt to set it will fail.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2691

 js/ui/keyboard.js | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/js/ui/keyboard.js b/js/ui/keyboard.js
index 56479a1b7e..d26fabc9f9 100644
--- a/js/ui/keyboard.js
+++ b/js/ui/keyboard.js
@@ -1257,6 +1257,10 @@ class Keyboard extends St.BoxLayout {
         return this._keyboardVisible && super.visible;
     }
 
+    set visible(visible) {
+        super.visible = visible;
+    }
+
     _onFocusPositionChanged(focusTracker) {
         let rect = focusTracker.getCurrentRect();
         this.setCursorLocation(focusTracker.currentWindow, rect.x, rect.y, rect.width, rect.height);