Currently we delete this metric "because it could differ from the sum of each goal conversions", but it should, since nb_visits_converted is not the sum of each goal's conversions. Conversions can happen multiple times per visit, so this would not be accurate.
Also, it is not the sum of each goals' nb_visits_converted, since visits can share conversions for different goals. Keeping it puts the correct value of conversion_rate in scheduled reports.
Moving to 3.11 since it's not a straightforward fix