rs: Fix the comment of build-interactive-process-graph.

It doesn't pad the context sequence with empty contexts any more.

rs.rkt

@@ -205,9 +205,7 @@
        [(state res '()) (set)]))])
 
 ;;; Builds the state graph of a reaction system driven by a given
-;;; context sequence.  When the context sequence is exhausted, keeps
-;;; running the system without contexts.  In other words, the context
-;;; sequence is padded with empty contexts at the end.
+;;; context sequence.
 (define (build-interactive-process-graph rs contexts)
   (dds-build-state-graph-annotated (dynamics rs)
                                    (set (state (set) contexts))))