CMake Deprecation Warning -- Update the VERSION argument <min> value or use the <min>...<max> syntax

[jrp2014]

When building mlx, I get this warning:

CMake Deprecation Warning at build/_deps/doctest-src/CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 3.10 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
  to tell CMake that the project requires at least <min> but has been updated
  to work with policies introduced by <max> or earlier.

Not critical, but the next time that someone has a reason to fiddle with the cmake file, this is something that could be silenced.

[zcbenz]

This comes from a dependency so I don't think we can fix it on our side, there was some efforts to fix in upstream but stalled: doctest/doctest#953.