[cmake] fix install directory for DuneUggridMacros.cmake
The install directory has to be ${DUNE_INSTALL_MODULEDIR}. Otherwise, the file will not be found by dune_process_dependency_macros from DuneMacros.cmake.
The install directory has to be ${DUNE_INSTALL_MODULEDIR}. Otherwise, the file will not be found by dune_process_dependency_macros from DuneMacros.cmake.