proto: add tds dummy (#7181)

Signed-off-by: Mike Schore <mike.schore@gmail.com>

Mirrored from https://github.com/envoyproxy/envoy @ 157f983d09bc0975d451d0b8426cc4262e26dfa1

envoy/service/discovery/v2/tds.proto

@@ -12,6 +12,11 @@ import "envoy/api/v2/discovery.proto";
 import "google/api/annotations.proto";
 import "google/protobuf/struct.proto";
 
+// [#not-implemented-hide:] Not configuration. Workaround c++ protobuf issue with importing
+// services: https://github.com/google/protobuf/issues/4221
+message TdsDummy {
+}
+
 // Discovery service for Runtime resources.
 // [#not-implemented-hide:]
 service RuntimeDiscoveryService {