Set required owncloud version to 4.93

This prevents the upgrade process from disabling all apps

@karlitschek @DeepDiver1975 

@karlitschek could you change make this change before you release a new version/beta for the next time (also in the apps repo)

(also see https://github.com/owncloud/apps/commit/ef8521e6cad958909c8a35927939f746bc76affa)