Optimize service_desk_enabled_projects counter in usage_data

# https://gitlab.com/gitlab-org/gitlab/-/blob/908902d1d4f6fbcd7780150c780837fd4fa8b301/ee/lib/ee/gitlab/usage_data.rb#L292
service_desk_enabled_projects: distinct_count(::Project.with_active_services.service_desk_enabled.where(time_period), :creator_id),

Part of !208233