Update configurable property syntax in EvtGen_i
No change in output expected.
(These changes were initially made as part of !58216 (merged), but were postponed until after the random seeding changes had gone through.)
Removing Generators/EvtGen_i/EvtGen_i/EvtDecay.h
and Generators/EvtGen_i/src/EvtDecay.cxx
, as this code is obsolete and was not being compiled anyway.
Edited by John Derek Chapman