Add note about spans being an experimental feature.

packages/telemetry/node-server-sdk-otel/src/TracingHook.ts

@@ -25,11 +25,14 @@ const TRACING_HOOK_NAME = 'LaunchDarkly Tracing Hook';
  */
 export interface TracingHookOptions {
   /**
-   * If set to true, then the tracing hook will add spans for each variation
+   * Experimental: If set to true, then the tracing hook will add spans for each variation
    * method call. Span events are always added and are unaffected by this
    * setting.
    *
    * The default value is false.
+   * 
+   * This feature is experimental and the data in the spans, or nesting of spans, 
+   * could change in future versions.
    */
   spans?: boolean;