Update ShannonIms CERTIFICATE to PRESIGNED for Lynx

This is a reland of 7f719af997a67e522aa400b36db05128d248b8dd which gets
lost in ag/25428572

Bug: 311289519
Change-Id: If9a1551e1e9f7c43b50881e180b91eb424ed2ec1

self-extractors/google_devices/staging/Android.mk.template

@@ -48,7 +48,7 @@ LOCAL_PRIVILEGED_MODULE := true
 LOCAL_MODULE_OWNER := samsung
 LOCAL_MODULE_CLASS := APPS
 LOCAL_SRC_FILES := $(LOCAL_MODULE).apk
-LOCAL_CERTIFICATE := platform
+LOCAL_CERTIFICATE := PRESIGNED
 LOCAL_LICENSE_KINDS := SPDX-license-identifier-Apache-2.0
 LOCAL_LICENSE_CONDITIONS := notice
 LOCAL_NOTICE_FILE := $(LOCAL_PATH)/../COPYRIGHT $(LOCAL_PATH)/../LICENSE