m/n/core/rpc: remove leftover local/external listener abstractions

This continues cleanup work after review.monogon.dev/624.

Change-Id: Ic38f4547627d382a4405cf4b3336aa7cac80849b
Reviewed-on: https://review.monogon.dev/c/monogon/+/629
Reviewed-by: Mateusz Zalega <mateusz@monogon.tech>
diff --git a/metropolis/node/core/rpc/server.go b/metropolis/node/core/rpc/server.go
index 0e823f4..97cb3ec 100644
--- a/metropolis/node/core/rpc/server.go
+++ b/metropolis/node/core/rpc/server.go
@@ -16,23 +16,11 @@
 	}
 )
 
-// ClusterExternalServices is the interface containing all gRPC services that a
-// Metropolis Cluster implements on its external interface. With the current
-// implementation of Metropolis, this is all implemented by the Curator.
-type ClusterExternalServices interface {
+// ClusterServices is the interface containing all gRPC services that a
+// Metropolis Cluster implements. With the current implementation of Metropolis,
+// this is all implemented by the Curator.
+type ClusterServices interface {
 	cpb.CuratorServer
 	apb.AAAServer
 	apb.ManagementServer
 }
-
-// ClusterInternalServices is the interface containing all gRPC services that a
-// Metropolis Cluster implements on its internal interface. Currently this is
-// just the Curator service.
-type ClusterInternalServices interface {
-	cpb.CuratorServer
-}
-
-type ClusterServices interface {
-	ClusterExternalServices
-	ClusterInternalServices
-}