Doc: Edit section title to not clash with an existing module name

A link to 'Qt 3D' may in some cases lead to a wrong page.

Change-Id: I7b05bcb7c31a63316c5936a165c72d83111f7783
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>
Reviewed-by: Martin Smith <martin.smith@qt.io>