docs: remove spurious comment marker

api/envoy/service/discovery/v3/discovery.proto

@@ -284,7 +284,7 @@ message Resource {
   // light-weight "heartbeat" updates to keep a resource with a TTL alive.
   //
   // The TTL feature is meant to support configurations that should be removed in the event of
-  // a management server // failure. For example, the feature may be used for fault injection
+  // a management server failure. For example, the feature may be used for fault injection
   // testing where the fault injection should be terminated in the event that Envoy loses contact
   // with the management server.
   google.protobuf.Duration ttl = 6;