Drop version constraint on FieldMap
Because of a bug in LbEnv, the version constraint on FieldMap was not taken into account. Now that the bug is fixed (lhcb-core/LbEnv!145 (merged)), we cannot run Moore or DaVinci jobs because we try to use FieldMap v5 (as Moore requires), but the CondDB says we should use the field map files field.v8r1.*.cdf, that, of course, exist only in FieldMap v8r1.
Removing the constraint on the version of FieldMap solves the problem reported in https://mattermost.web.cern.ch/lhcb/pl/an8q4mma778mzyn9zwsanw8apr