Remove settings_keys.h from qt4_wrap_cpp to suppress warning

There are no QT-wrappable classes in this header, so the QT build emits a
warning that it's doing nothing on the file. Since it's doing nothing,
we might as well remove the file from the wrapper macro.

CMakeLists.txt

@@ -32,8 +32,7 @@ file (GLOB HEADER_FILES
   include/swri_console/log_database.h
   include/swri_console/node_list_model.h
   include/swri_console/log_database_proxy_model.h
-  include/swri_console/ros_thread.h
-  include/swri_console/settings_keys.h)
+  include/swri_console/ros_thread.h)
 file (GLOB SRC_FILES
   src/bag_reader.cpp
   src/console_master.cpp