Update POSButtonVariant to fileprivate now that it is an implementation detail.

Author: jaclync

WooCommerce/Classes/POS/Presentation/Reusable Views/Buttons/POSButtonStyle.swift

@@ -1,11 +1,5 @@
 import SwiftUI
 
-/// The visual variant of the POS button.
-enum POSButtonVariant {
-    case filled
-    case outlined
-}
-
 /// The size variant of the POS button.
 enum POSButtonSize {
     case normal
@@ -40,6 +34,12 @@ struct POSOutlinedButtonStyle: ButtonStyle {
     }
 }
 
+/// The visual variant of the POS button.
+fileprivate enum POSButtonVariant {
+    case filled
+    case outlined
+}
+
 private struct POSButton: View {
     @Environment(\.isEnabled) var isEnabled