Fix build on ARM64EC (#2858)

Remove `#pragma intrinsic(_umul128)` because it doesn't work on
ARM64EC and x64 works without it.

Co-authored-by: Agoston Szepessy <agos@microsoft.com>

src/catch2/internal/catch_random_integer_helpers.hpp

@@ -39,7 +39,6 @@
     !defined( CATCH_CONFIG_MSVC_UMUL128 )
 #    define CATCH_CONFIG_MSVC_UMUL128
 #    include <intrin.h>
-#    pragma intrinsic( _umul128 )
 #endif