Change the bubble bar flag in wms to a getter.

I accidentally removed it from cl/24904944 before I uploaded the CL.

Bug: 273994695
Test: Manual:
       - turn flag off
       - create bubbles
       - observe floating bubbles are added
       - turn flag on
       - change navigation mode to gesture navigation
       - observe bubble bar becomes visible
Change-Id: If7fee02e026eece1bc9378248a622d601e4f764f
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/bubbles/properties/ProdBubbleProperties.kt b/libs/WindowManager/Shell/src/com/android/wm/shell/bubbles/properties/ProdBubbleProperties.kt
index 67dc642..e1dea3b 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/bubbles/properties/ProdBubbleProperties.kt
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/bubbles/properties/ProdBubbleProperties.kt
@@ -25,7 +25,8 @@
     private var _isBubbleBarEnabled =
             SystemProperties.getBoolean("persist.wm.debug.bubble_bar", false)
 
-    override val isBubbleBarEnabled = _isBubbleBarEnabled
+    override val isBubbleBarEnabled
+        get() = _isBubbleBarEnabled
 
     override fun refresh() {
         _isBubbleBarEnabled = SystemProperties.getBoolean("persist.wm.debug.bubble_bar", false)