deleted a needless reference to rtrancl_unfold

--- a/doc-src/TutorialI/Sets/Relations.thy	Mon May 28 18:48:28 2001 +0200
+++ b/doc-src/TutorialI/Sets/Relations.thy	Tue May 29 11:43:12 2001 +0200
@@ -60,9 +60,6 @@
 @{thm[display] relpow.simps[no_vars]}
 \rulename{relpow.simps}
 
-@{thm[display] rtrancl_unfold[no_vars]}
-\rulename{rtrancl_unfold}
-
 @{thm[display] rtrancl_refl[no_vars]}
 \rulename{rtrancl_refl}