PWGGA/GammaConv: better binning and trainconfigs

[sstiefel19]

No description provided.

[alibuild]

a8d3725: approval required: 1 of @FriederikeBock (Friederike Bock), @chiarazampolli (Chiara Zampolli), @davidrohr (David Rohr), @fjonasALICE (Florian Jonas), @gconesab (Gustavo Conesa Balbastre), @jgrosseo (Jan Fiete Grosse-Oetringhaus), @jokonig (Joshua Leon Konig), @kharlov (Yuri Kharlov), @ktf (Giulio Eulisse), @loizides (Constantinos Loizides), @mikesas (Mike Henry Petrus Sas), @nschmidtALICE (Nicolas Vincent Schmidt), @peressounko (Dmitri Peresunko), @policheh (Boris Polishchuk), @pzhristov (Peter Hristov), @qgp (Jochen Klein), @sawenzel (Sandro Christian Wenzel), @shahor02 (Ruben Shahoyan)

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