Remove deprecated enable_rkpd property

The enable_rkpd property is no longer needed. This change removes the
vestigial property.

Test: Successful build
Change-Id: I810d5a21cbe01b43a37244959e21febd0880be59
diff --git a/private/property_contexts b/private/property_contexts
index 19bd51a..44d5ad3 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -1422,9 +1422,6 @@
 # Hostname for the remote provisioning server a device should communicate with
 remote_provisioning.hostname u:object_r:remote_prov_prop:s0 exact string
 
-# Indicates the system should use rkpd instead of RemoteProvisioner
-remote_provisioning.enable_rkpd u:object_r:remote_prov_prop:s0 exact bool
-
 # Broadcast boot stages, which keystore listens to
 keystore.boot_level u:object_r:keystore_listen_prop:s0 exact int