Fix stack education showing every time

A small regression from the recent migration changes.

Test: manual - new flash, post some bubbles, notice you see stack
               education for first tap on the stack but not subsequent taps
Bug: 161980186

Change-Id: Ia3fda22e002a3cdbef085ceb6c1d7dd58e1d939a

packages/SystemUI/src/com/android/systemui/bubbles/StackEducationView.kt

@@ -128,7 +128,7 @@ class StackEducationView constructor(context: Context) : LinearLayout(context) {
 
     private fun setShouldShow(shouldShow: Boolean) {
         context.getSharedPreferences(context.packageName, Context.MODE_PRIVATE)
-                .edit().putBoolean(PREF_MANAGED_EDUCATION, !shouldShow).apply()
+                .edit().putBoolean(PREF_STACK_EDUCATION, !shouldShow).apply()
     }
 }