Don't output floats in prime example.

Doc/tutorial/controlflow.rst

@@ -166,7 +166,7 @@ following loop, which searches for prime numbers::
    >>> for n in range(2, 10):
    ...     for x in range(2, n):
    ...         if n % x == 0:
-   ...             print(n, 'equals', x, '*', n/x)
+   ...             print(n, 'equals', x, '*', n//x)
    ...             break
    ...     else:
    ...         # loop fell through without finding a factor