CMake: Removed duplicate line for configuration.hpp

CMakeLists.txt

@@ -71,7 +71,6 @@ set(LIBDATACHANNEL_HEADERS
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/candidate.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/channel.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/configuration.hpp
-	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/configuration.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/datachannel.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/description.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/mediahandler.hpp