Don't sign auto-generated RROs with platform cert

Preinstalled overlays needn't be signed with the same cert
as the package it overlays, simply being preinstalled is
enough. Sign with the default cert instead for now, which
provides fewer special privileges.

Bug: 129373833
Test: internal overlay test
Change-Id: Ie18f7ff749e3f079600f74203664bcb6d11f9d6a
diff --git a/core/generate_enforce_rro.mk b/core/generate_enforce_rro.mk
index f7877f2..6a23aeb 100644
--- a/core/generate_enforce_rro.mk
+++ b/core/generate_enforce_rro.mk
@@ -34,7 +34,6 @@
 endif
 
 LOCAL_FULL_MANIFEST_FILE := $(rro_android_manifest_file)
-LOCAL_CERTIFICATE := platform
 
 LOCAL_AAPT_FLAGS += --auto-add-overlay
 LOCAL_RESOURCE_DIR := $(enforce_rro_source_overlays)