[Build] Finalise switch from UG to dune-uggrid

src/CMakeLists.txt

@@ -40,6 +40,3 @@ foreach(_dim 2 3)
   set_property(TARGET ${_sw_target} APPEND PROPERTY COMPILE_DEFINITIONS "MY_DIM=${_dim}")
   set_property(TARGET ${_ugw_target} APPEND PROPERTY COMPILE_DEFINITIONS "MY_DIM=${_dim}")
 endforeach()
-
-# Mark UG as required
-find_package(UG REQUIRED)