[TimePicker] Fix color of unselected state in AM/PM picker.

Specs:  https://m3.material.io/components/time-pickers/specs
PiperOrigin-RevId: 631920571

lib/java/com/google/android/material/timepicker/res/color/m3_timepicker_button_background_color.xml

@@ -16,5 +16,5 @@
 -->
 <selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:color="@macro/m3_comp_time_picker_period_selector_selected_container_color" android:state_enabled="true" android:state_checked="true"/>
- <item android:color="?attr/colorSurface" android:state_checked="false"/>
+ <item android:color="@android:color/transparent" android:state_checked="false"/>
 </selector>