Fix compilation of GeneratorFilters package in master--HepMC3 nightly
Linking against AtlasHepMCsearchLib
was lost as part !58146 (merged). This is needed for compilation in the master--HepMC3 nightly, so adding it back.
Linking against AtlasHepMCsearchLib
was lost as part !58146 (merged). This is needed for compilation in the master--HepMC3 nightly, so adding it back.