This update for HepMC fixes the following issues:

HepMC was updated to version 3.2.2:

* Fixed treatment of the weights in case of different number of
  weights and weight names.
* Fixed WriterAsciiHepMC2 option for separate flows.
* Improved treatment of python installation.
* Split the sources of python bindings into smaller files to
  optimize compilation.
* Improved cmake configuration for special cases, e.g. old
  cmake, no ROOT, some compilers, etc. Added more error
  handling.
* Fixed compilation of the search module with Clang.
* Added an example for search module.
* Fixed the HepMC2 output for events without weights.
* Fixed the signal vertex ID for HepMC2 output.
* Added an interface for HepMC2 (in-memory-conversion).
* Added functions to search module: search for relatives
  (particle or vertex)->(particle or vertex) in different
  combinations.
* The previous point bumps .so version of the libHepMC3search to
  4.
* Improved the configuration of Pythia8 for tests (minimal
  version requirement).
* Fixed compatibility of ROOT trees written with HePMC3.0 and
  removed the typedefs in the dictionaries.

This update was imported from the openSUSE:Leap:15.2:Update update project.