sage.categories.finite_fields: don't import from integer_ring

Importing ZZ from the integer ring creates an import cycle,

  integer_ring -> integer
               -> rational
               -> rational_field
               -> categories/finite_fields
               -> integer_ring

I noticed this because the cycle has started causing an ImportError
when I attempt to import ZZ. This commit doesn't fix the problem
(there are other cycles), but it is minimally invasive and does
improve the import graph a tiny bit.

Author: orlitzky

src/sage/categories/finite_fields.py

@@ -16,7 +16,6 @@
 from sage.categories.category_with_axiom import CategoryWithAxiom
 from sage.categories.enumerated_sets import EnumeratedSets
 from sage.rings.integer import Integer
-from sage.rings.integer_ring import ZZ
 from sage.misc.cachefunc import cached_method
 
 
@@ -332,7 +331,7 @@ def _tonelli(self):
             if not self.is_square():
                 raise ValueError("element is not a square")
             g = self.parent().quadratic_nonresidue()
-            even_exp, odd_order = (q - ZZ.one()).val_unit(2)
+            even_exp, odd_order = (q - Integer(1)).val_unit(2)
             e = 0
             for i in range(2, even_exp+1):
                 tmp = self * (pow(g, -e))