Update PreferenceCategory headers to use headline font.

Medium version.

Bug: 70296667
Test: visual
Change-Id: Ic4e67d4adbdde52822751d28ca50db446fc59a1e
diff --git a/res/layout/preference_category_material_settings.xml b/res/layout/preference_category_material_settings.xml
index 81ee58d..d815946 100644
--- a/res/layout/preference_category_material_settings.xml
+++ b/res/layout/preference_category_material_settings.xml
@@ -50,6 +50,7 @@
             android:layout_marginTop="16dp"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
+            android:fontFamily="@*android:string/config_headlineFontFamilyMedium"
             android:textAppearance="@android:style/TextAppearance.Material.Body2"
             android:textColor="?android:attr/colorAccent"
             android:paddingEnd="?android:attr/listPreferredItemPaddingEnd"/>