Remove `tabular_policy_from_policy`, which is unused.
Remove `tabular_policy_from_policy`, which is unused.

PiperOrigin-RevId: 309899103
Change-Id: I839944db76026c6d774ef9cb9f1b2aeaef609baf

deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel,deepmind/open_spiel