Fix trailing whitespace

Doc/library/xml.etree.elementtree.rst

@@ -390,7 +390,7 @@ Functions
    Note that while :func:`iterparse` builds the tree incrementally, it issues
    blocking reads on *source* (or the file it names).  As such, it's unsuitable
    for asynchronous applications where blocking reads can't be made.  For fully
-   asynchronous parsing, see :class:`IncrementalParser`. 
+   asynchronous parsing, see :class:`IncrementalParser`.
 
    .. note::