fixed numVertices in transitive closure example

Author: Udo Klein <git@blinkenlight.net>

Closes #10642 from udoklein/patch-2.

examples/src/main/python/transitive_closure.py

@@ -30,8 +30,8 @@ rand = Random(42)
 def generateGraph():
     edges = set()
     while len(edges) < numEdges:
-        src = rand.randrange(0, numEdges)
-        dst = rand.randrange(0, numEdges)
+        src = rand.randrange(0, numVertices)
+        dst = rand.randrange(0, numVertices)
         if src != dst:
             edges.add((src, dst))
     return edges