py3: use range instead of xrange in tests/test-issue4074.t

xrange in not present on Python 3.

Differential Revision: https://phab.mercurial-scm.org/D2329

tests/test-issue4074.t

@@ -4,7 +4,7 b' A script to generate nasty diff worst-ca'
 
   $ cat > s.py <<EOF
   > import random
-  > for x in xrange(100000):
+  > for x in range(100000):
   >     print
   >     if random.randint(0, 100) >= 50:
   >         x += 1