jQuery.removeData: document it returns undefined

Not to be confused with the `removeData` method, which does return
a jQuery collection.

Fixes jquery#1153
Closes jquery#1154

Author: edg2s

entries/jQuery.removeData.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<entry type="method" name="jQuery.removeData" return="jQuery">
+<entry type="method" name="jQuery.removeData" return="undefined">
   <title>jQuery.removeData()</title>
   <signature>
     <added>1.2.3</added>