update env example

shards/mishards/.env.example

@@ -12,8 +12,10 @@ SQL_ECHO=True
 SQLALCHEMY_DATABASE_TEST_URI=sqlite:////tmp/milvus/db/meta.sqlite?check_same_thread=False
 SQL_TEST_ECHO=False
 
+TRACER_PLUGIN_PATH=/tmp/plugins
+
 # TRACING_TEST_TYPE=jaeger
-TRACING_TYPE=jaeger
+TRACER_CLASS_NAME=jaeger
 TRACING_SERVICE_NAME=fortest
 TRACING_SAMPLER_TYPE=const
 TRACING_SAMPLER_PARAM=1
@@ -21,9 +23,6 @@ TRACING_LOG_PAYLOAD=True
 #TRACING_SAMPLER_TYPE=probabilistic
 #TRACING_SAMPLER_PARAM=0.5
 
-TRACER_PLUGIN_PATH=/tmp/plugins
-# TRACER_CLASS_NAME=
-
 #DISCOVERY_PLUGIN_PATH=
 #DISCOVERY_CLASS_NAME=kubernetes