Revert "Fix team_info::side_name() returning wrong type"

This reverts commit 89ef1d3.

That commit made side_name() return a wrong value in case
current_player changed during a game.

src/team.cpp

@@ -127,9 +127,6 @@ void team::team_info::read(const config &cfg)
 	side_name = cfg["side_name"];
 	save_id = cfg["save_id"].str();
 	current_player = cfg["current_player"].str();
-	if(side_name.empty()) {
-		side_name = current_player;
-	}
 	countdown_time = cfg["countdown_time"].str();
 	action_bonus_count = cfg["action_bonus_count"];
 	flag = cfg["flag"].str();

src/team.hpp

@@ -303,7 +303,7 @@ class team : public savegame::savegame_config
 	void set_flag(const std::string& flag) { info_.flag = flag; }
 	void set_flag_icon(const std::string& flag_icon) { info_.flag_icon = flag_icon; }
 
-	const t_string& side_name() const { return info_.side_name; }
+	const std::string& side_name() const { return info_.side_name.empty() ? info_.current_player : info_.side_name.str(); }
 	//Returns true if the hex is shrouded/fogged for this side, or
 	//any other ally with shared vision.
 	bool shrouded(const map_location& loc) const;