refactor: remove misleading build warning

* Among other issues, this message is often misinterpreted by users
  building out-of-tree shields -- leading them to think the shield
  "not being found" is the cause of a build failure.

app/keymap-module/modules/modules.cmake

@@ -97,7 +97,6 @@ foreach(root ${BOARD_ROOT})
     if(DEFINED SHIELD)
         foreach(s ${SHIELD_AS_LIST})
             if(NOT ${s} IN_LIST SHIELD_LIST)
-                message(WARNING "Didn't find ${s}")
                 continue()
             endif()
             message(STATUS "Adding ${SHIELD_DIR_${s}}")