Cleaned up a few game_config_manager.hpp includes

src/game_initialization/configure_engine.cpp

@@ -14,7 +14,6 @@
 #include "game_initialization/configure_engine.hpp"
 
 #include "formula/string_utils.hpp"
-#include "game_config_manager.hpp"
 #include "mp_game_settings.hpp"
 #include "preferences/credentials.hpp"
 #include "preferences/game.hpp"

src/gui/dialogs/game_ui.cpp

@@ -25,7 +25,6 @@
 
 #include "display.hpp"
 #include "formula/variant.hpp"
-#include "game_config_manager.hpp"
 #include "gettext.hpp"
 
 namespace gui2

src/gui/dialogs/multiplayer/faction_select.cpp

@@ -30,7 +30,6 @@
 #include "gui/widgets/toggle_button.hpp"
 #include "gui/widgets/window.hpp"
 #include "formatter.hpp"
-#include "game_config_manager.hpp"
 #include "gettext.hpp"
 #include "help/help.hpp"
 #include "preferences/game.hpp"	// for encountered_units