Simplify xAOD::TPyEvent so the new cppyy can handle it. ATEAM-980
xAOD::TPyEvent was inheriting all TEvent constructors and that confused
the new cppyy in ROOT 6.32 when python TPyEvent class was inheriting
from xAOD::TPyEvent.
I am leaving only the default TPyEvent constructor as it seems to be the
only one actually used by the python side.
All tests failing in ROOT.32 are tracked in ATEAM-980
Edited by Marcin Nowak