This commit includes two changes to the *.desktop file:
1. Adds the Bisq version number.
2. Fixes the categories.
Sometimes the Bisq network raises the minimum required Bisq version. Adding the version number so that it's displayed in the desktop environment's menu makes it easy for users to confirm whether they have the necessary version.
Originally, there were two main categories assigned, which violates the standard. This change removes one of the main categories and adds an auxillary category.