remove import

Author: fchapoton

src/sage/rings/finite_rings/integer_mod_ring.py

@@ -67,7 +67,7 @@
 from sage.arith.misc import factor
 from sage.arith.misc import primitive_root
 from sage.arith.misc import CRT_basis
-from sage.rings.ring import Field, CommutativeRing
+from sage.rings.ring import Field
 from sage.misc.mrange import cartesian_product_iterator
 import sage.rings.abc
 from sage.rings.finite_rings import integer_mod