Fix docstring markup in sage/game_theory #34156
Description
Part of #34157:
sage/game_theory/normal_form_game.py:2345:1: RST201 Block quote ends without a blank line; unexpected unindent.
sage/game_theory/normal_form_game.py:2346:1: RST213 Inline emphasis start-string without end-string.
sage/game_theory/normal_form_game.py:2346:1: RST213 Inline emphasis start-string without end-string.
sage/game_theory/normal_form_game.py:2361:1: RST213 Inline emphasis start-string without end-string.
Component: documentation
Author: Frédéric Chapoton
Branch/Commit: 279391c
Reviewer: Matthias Koeppe
Issue created by migration from https://trac.sagemath.org/ticket/34156