Fix a wrong folder name about optional reporter (#685)

Author: JoeCqupt

docs/en/setup/service-agent/java-agent/advanced-reporters.md

@@ -1,5 +1,5 @@
 # Advanced Reporters
-The advanced report provides an alternative way to submit the agent collected data to the backend. All of them are in the `optional-reporter-plugins` folder, move the one you needed into the `reporter-plugins` folder for the activation. **Notice, don't try to activate multiple reporters, that could cause unexpected fatal errors.**
+The advanced report provides an alternative way to submit the agent collected data to the backend. All of them are in the `optional-reporter-plugins` folder, move the one you needed into the `plugins` folder for the activation. **Notice, don't try to activate multiple reporters, that could cause unexpected fatal errors.**
 
 ## Kafka Reporter
 The Kafka reporter plugin support report traces, JVM metrics, Instance Properties, and profiled snapshots to Kafka cluster, which is disabled in default. Move the jar of the plugin, `kafka-reporter-plugin-x.y.z.jar`, from `agent/optional-reporter-plugins` to `agent/plugins` for activating.