[audioplugins] fix stale Discovered state comment

persistDiscoveredPlaceholders() produces the Discovered state (the
validate-later flow), so it is no longer 'reserved with no producer'.

Author: luapmartin

framework/audioplugins/audiopluginstypes.h

@@ -113,9 +113,10 @@ inline int intAttribute(const PluginMeta& meta, const String& key, int fallback
 }
 
 // Lifecycle state of a plugin entry in the cache.
-//   Discovered: scanner found the file at `path`; validation has not yet completed.
-//               (Reserved: no producer in the framework yet — apps that want a
-//                pre-validation insertion flow can transition to this state.)
+//   Discovered: scanner found the file at `path`; validation has not yet
+//               completed. RegisterAudioPluginsScenario::persistDiscoveredPlaceholders()
+//               writes these when paths are registered with validate=false (the
+//               "validate later" flow); scanPlugins() re-validates them later.
 //   Validated:  validation succeeded; the plugin is usable.
 //   Missing:    `path` was known previously but the scanner no longer finds it.
 //   Error:      validation failed; `errorCode` carries the details.