[docs] Upgrade qhelgenerator.

Author: hageboeck

documentation/doxygen/Doxyfile

@@ -1700,7 +1700,7 @@ QHP_SECT_FILTER_ATTRS  =
 # run qhelpgenerator on the generated .qhp file.
 # This tag requires that the tag GENERATE_QHP is set to YES.
 
-QHG_LOCATION           = qhelpgenerator-qt5
+QHG_LOCATION           = qhelpgenerator
 
 # If the GENERATE_ECLIPSEHELP tag is set to YES, additional index files will be
 # generated, together with the HTML files, they form an Eclipse help plugin. To