add DD_DISCOVERY_SERVICE_ENABLED to config_norm_rules.json

Author: lucaspimentel

tracer/test/Datadog.Trace.Tests/Telemetry/config_norm_rules.json

@@ -309,6 +309,7 @@
   "dbm_propagation_mode": "dbm_propagation_mode",
   "trace.remove_root_span_laravel_queue": "trace_remove_root_span_laravel_queue_enabled",
   "trace.remove_autoinstrumentation_orphans": "trace_remove_auto_instrumentation_orphans_enabled",
+  "DD_DISCOVERY_SERVICE_ENABLED": "discovery_service_enabled",
   "DD_TRACE_AWS_ADD_SPAN_POINTERS": "trace_aws_add_span_pointers",
   "DD_TRACE_CONFIG_FILE": "trace_config_file",
   "DD_DOTNET_TRACER_CONFIG_FILE": "trace_config_file",