Add platform certificate to Notes Role enable RRO

Bug: 284124708
Change-Id: I2322d8486f147786bddd57ad4ef1bea6a33eb535
Test: just config change
diff --git a/packages/overlays/NotesRoleEnabledOverlay/Android.bp b/packages/overlays/NotesRoleEnabledOverlay/Android.bp
index 68ebd96..70b783f 100644
--- a/packages/overlays/NotesRoleEnabledOverlay/Android.bp
+++ b/packages/overlays/NotesRoleEnabledOverlay/Android.bp
@@ -25,6 +25,7 @@
 
 runtime_resource_overlay {
     name: "NotesRoleEnabledOverlay",
+    certificate: "platform",
     theme: "NotesRoleEnabled",
     product_specific: true,
 }