Update default LHCbCond tag for 2018
Updates default LHCbCond tag for 2018 to cond-20181204-1, lhcb-conddb/LHCBCOND!29 (merged) (Reduce lumi thresholds to minimum for 2018 heavy ions)
Cherry-picked from !1656 (merged) in 2018-patches
Updates default LHCbCond tag for 2018 to cond-20181204-1, lhcb-conddb/LHCBCOND!29 (merged) (Reduce lumi thresholds to minimum for 2018 heavy ions)
Cherry-picked from !1656 (merged) in 2018-patches