Removed single trailing whitespace.

Author: Alex-Wasowicz

Doc/reference/datamodel.rst

@@ -323,7 +323,7 @@ to negative slice positions.
 
 Some sequences also support "extended slicing" with a third *step* parameter:
 ``a[start:stop:step]`` selects all items of *a* with index *i*, where
-``i = start + n*step`` and ``0 <= n``, such that ``start <= i < stop`` for 
+``i = start + n*step`` and ``0 <= n``, such that ``start <= i < stop`` for
 ``0 <= step``, and ``stop < i <= start`` for ``step < 0``.
 
 Slicing parameters can be omitted: