Fix punctuation.

Doc/library/xml.etree.elementtree.rst

@@ -529,5 +529,5 @@ This is an example of counting the maximum depth of an XML file::
 .. [#] The encoding string included in XML output should conform to the
    appropriate standards. For example, "UTF-8" is valid, but "UTF8" is
    not. See http://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl
-   and http://www.iana.org/assignments/character-sets .
+   and http://www.iana.org/assignments/character-sets.