Doc: Update examplesinstallpath to include the repository name

The examplesinstallpath variable in .qdocconf files defines the path
under QT_INSTALL_EXAMPLES where examples are found.

To match the way examples are packaged in Qt 5.6, prefix the
install path with the repository name.

Task-number: QTBUG-48736
Change-Id: I51119245c1799dd228ab2fd0191e6f08b81a304b
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>

src/imports/qtcanvas3d/doc/qtcanvas3d.qdocconf

@@ -11,7 +11,7 @@ imagedirs  += images
 headerdirs += ..
 sourcedirs += ..
 
-examplesinstallpath = canvas3d
+examplesinstallpath = qtcanvas3d/canvas3d
 
 depends     = qtcore qtgui qtqml qtquick qtquickcontrols qtquicklayouts qtdoc qtmultimedia