turtledemo/penrose.py: remove unused clock() calls (GH-10033)

Actually time calculations were remove in commit 891a1f8.
diff --git a/Lib/turtledemo/penrose.py b/Lib/turtledemo/penrose.py
index e118d6a..045722a 100755
--- a/Lib/turtledemo/penrose.py
+++ b/Lib/turtledemo/penrose.py
@@ -137,13 +137,10 @@
     goto(startpos)
     setheading(0)
     tiledict = {}
-    a = clock()
     tracer(0)
     fun(l, n)
-    b = clock()
     draw(l, n, th)
     tracer(1)
-    c = clock()
     nk = len([x for x in tiledict if tiledict[x]])
     nd = len([x for x in tiledict if not tiledict[x]])
     print("%d kites and %d darts = %d pieces." % (nk, nd, nk+nd))