doc: Eliminate even more cases of multiple topic commands

This fixes the examples in publish and subscribe.
Two instances where \page and \example occurred in
the same comment were corrected by removing the
\page and leaving the \example. The group page
for publish and subscribe was also corrected.

Task-number: QTBUG-31578
Change-Id: I7f5ab3384e73171a942719f841a6481ae0b216f2
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>