add a space at eof

Author: lindseymoore

source/indexes/single-field-index.txt

@@ -132,4 +132,4 @@ following API documentation:
 
 - `indexes <{+api-root+}/Mongo/Collection.html#indexes-instance_method>`__
 - `create_one <{+api-root+}/Mongo/Index/View.html>`__
-- `find <{+api-root+}/Mongo/Collection.html#find-instance_method>`__ 
+- `find <{+api-root+}/Mongo/Collection.html#find-instance_method>`__