Restore system card context menu preview

TFI/UI/Managed/MobileCards.swift

@@ -151,8 +151,6 @@ struct MobileActionCard<Content: View, Actions: View>: View {
             cardSurface
                 .contextMenu {
                     actions
-                } preview: {
-                    cardSurface
                 }
         }
         .buttonStyle(.plain)

TFITests/MobileNavigationParityTests.swift

@@ -185,7 +185,7 @@ struct MobileNavigationParityTests {
         #expect(cards.contains(".contentShape([.interaction, .contextMenuPreview], shape)"))
         #expect(cards.contains(".containerShape("))
         #expect(!cards.contains(".contentShape(.rect)"))
-        #expect(cards.contains("} preview: {\n                    cardSurface"))
+        #expect(!cards.contains("} preview: {"))
         #expect(!cards.contains("sourceSize"))
         #expect(!cards.contains(".frame(width: 320"))