Trac #20195: Minor documentation bug in limit

The `dir='above'` option for `limit` has been deprecated since #9200,
but the first example in the docstring still uses it, instead of
`dir='+'`.

URL: http://trac.sagemath.org/20195
Reported by: embray
Ticket author(s): Eric Bray
Reviewer(s): Frédéric Chapoton

src/sage/calculus/calculus.py

@@ -987,7 +987,7 @@ def limit(ex, dir=None, taylor=False, algorithm='maxima', **argv):
     ::
 
        expr.limit(x = a)
-       expr.limit(x = a, dir='above')
+       expr.limit(x = a, dir='+')
 
     INPUT: