Add clarifying documentation line for edge case

client/client.go

@@ -137,7 +137,8 @@ type OpAMPClient interface {
 
 	// SetAvailableComponents modifies the set of components that are available for configuration
 	// on the agent.
-	// If called before Start(), initializes the client state that will be sent to the server upon Start().
+	// If called before Start(), initializes the client state that will be sent to the server upon
+	// Start() if the if the ReportsAvailableComponents capability is set.
 	// Must be called before Start() if the ReportsAvailableComponents capability is set.
 	//
 	// May be called any time after Start(), including from the OnMessage handler.