[cmake] drop feature detection of `std::make_unique`

cmake/modules/CheckCXXFeatures.cmake

@@ -523,12 +523,6 @@ check_include_file_cxx(
   DUNE_HAVE_HEADER_EXPERIMENTAL_TYPE_TRAITS
   )
 
-check_cxx_symbol_exists(
-  "std::make_unique<int>"
-  memory
-  DUNE_HAVE_CXX_MAKE_UNIQUE
-  )
-
 check_cxx_symbol_exists(
   "std::move<std::bool_constant<true>>"
   "utility;type_traits"

config.h.cmake

@@ -41,9 +41,6 @@
 /* does the standard library provide <experimental/type_traits> ? */
 #cmakedefine DUNE_HAVE_HEADER_EXPERIMENTAL_TYPE_TRAITS 1
 
-/* does the standard library provide make_unique() ? */
-#cmakedefine DUNE_HAVE_CXX_MAKE_UNIQUE 1
-
 /* does the standard library provide bool_constant ? */
 #cmakedefine DUNE_HAVE_CXX_BOOL_CONSTANT 1