Update JSON logging note in Java config

Clarify that JSON logging setting does not support environment variables.

Author: brett0000FF

content/en/tracing/trace_collection/library_config/java.md

@@ -210,7 +210,8 @@ When `true`, debug mode for the Datadog Java Tracer is enabled.
 `datadog.slf4j.simpleLogger.jsonEnabled`
 : **Environment Variable**: Not available<br>
 **Default**: `false`<br>
-When `true`, Datadog Java tracer logs are written in JSON. Available for versions 1.48.0+.
+When `true`, Datadog Java tracer logs are written in JSON. Available for versions 1.48.0+.<br>
+**Note**: This setting is specific to the embedded SLF4J simple logger and does not support environment variables. `dd.log.format.json` is the preferred configuration option.
 
 `dd.trace.servlet.principal.enabled`
 : **Environment Variable**: `DD_TRACE_SERVLET_PRINCIPAL_ENABLED`<br>