Fixing androidx preference fragments not being preserved by proguard

Bug: 119122391
Change-Id: Ib41010d4ac5f79a14a2b132ed723ad92580bc405
diff --git a/proguard.flags b/proguard.flags
index bb52a6c..eb27737 100644
--- a/proguard.flags
+++ b/proguard.flags
@@ -24,7 +24,7 @@
 -keep class androidx.recyclerview.widget.RecyclerView { *; }
 
 # Preference fragments
--keep class ** extends android.preference.PreferenceFragment {
+-keep class ** extends android.app.Fragment {
     public <init>(...);
 }