lib: remove unused header

This an unused header with empty class. Just remove it.

cmake_modules/VCMI_lib.cmake

@@ -239,8 +239,6 @@ macro(add_main_lib TARGET_NAME LIBRARY_TYPE)
 		${MAIN_LIB_DIR}/../include/vcmi/Environment.h
 		${MAIN_LIB_DIR}/../include/vcmi/Services.h
 
-		${MAIN_LIB_DIR}/abilities/Ability.h
-
 		${MAIN_LIB_DIR}/battle/AccessibilityInfo.h
 		${MAIN_LIB_DIR}/battle/BattleAction.h
 		${MAIN_LIB_DIR}/battle/BattleAttackInfo.h

lib/VCMI_lib.cbp

@@ -281,7 +281,6 @@
 		<Unit filename="VCMIDirs.h" />
 		<Unit filename="VCMI_Lib.cpp" />
 		<Unit filename="VCMI_Lib.h" />
-		<Unit filename="abilities/Ability.h" />
 		<Unit filename="battle/AccessibilityInfo.cpp" />
 		<Unit filename="battle/AccessibilityInfo.h" />
 		<Unit filename="battle/BattleAction.cpp" />

lib/abilities/Ability.h

@@ -1,23 +0,0 @@
-/*
- * Ability.h, part of VCMI engine
- *
- * Authors: listed in file AUTHORS in main folder
- *
- * License: GNU General Public License v2.0 or later
- * Full text of license available in license.txt file, in main folder
- *
- */
-
-VCMI_LIB_NAMESPACE_BEGIN
-
-namespace abilities
-{
-
-class DLL_LINKAGE Ability
-{
-
-};
-
-}
-
-VCMI_LIB_NAMESPACE_END