When freezing framework manifests, use aosp_arm64 target

We want to use GSI targets because they will contain the expected
framework manifests in order to remain backwards compatibile.
New launching devices may choose to remove some of the services like

Test: NA
Bug: 218588089
Change-Id: Iae4abb43a8c4a2e535ff961418fa4139506792cd
diff --git a/vintfdata/README.md b/vintfdata/README.md
index cfc1da7..6116757 100644
--- a/vintfdata/README.md
+++ b/vintfdata/README.md
@@ -70,7 +70,7 @@
 Execute the following, replacing the argument with the level to freeze:
 ```shell script
-lunch cf_x86_phone-userdebug # or any generic target
+lunch aosp_arm64
 ./freeze.sh ${LEVEL}