Doc: remove space from value of project variable

This is a new qdoc requirement for the project variable in
qdocconf files.

Change-Id: I23d921bac68e3c2948c4193b08a60c756e258ccc
Reviewed-by: Casper van Donderen <casper.vandonderen@nokia.com>

doc/config/qtcreator-project.qdocconf

-project     = "Qt Creator"
+project     = "QtCreator"
 description = "Qt Creator Manual"
 
 headerdirs =