Bump MaintenanceTool version

Bump version to allow for an update that enables proxy settings, again.

Jump directly to revision 3 to be in line with the installer name.
(That one got a version -2 because of a missing recompile).

Task-number: QTBUG-39164
Change-Id: I78a7058b80e88f57ec19b77b677670621183ea82
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>