Compose RELEASE_SERVICE_VERSION into knavalbattle version number

Summary:
version was increased to 2.1 "recently" and not so many changes have been done since them
so asserting the verison number is stuck in the past is a bit too much, but still having it move with
each new release is important for reproducibility of issues, etc. so compromise and append the version at the end

Reviewers: #kde_games

Subscribers: kde-games-devel

Differential Revision: https://phabricator.kde.org/D27754