Fix missing text on Index documentation page.

Author: graingert

pandas/core/index.py

@@ -1583,7 +1583,7 @@ def map(self, mapper):
     def isin(self, values, level=None):
         """
         Compute boolean array of whether each index value is found in the
-        passed set of values
+        passed set of values.
 
         Parameters
         ----------