Set policy_max to 3.10 in cmake_minimum_required to support CMake 4.0

[traversaro]

Current flann fails configuration in CMake 4.0 with error:

CMake Error at CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 3.5 has been removed from 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.

  Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.

Bumping just the policy_max to 3.10 ensures that there are no errors or warnings when configuring with CMake 4.0, while keeping the existing compatibility with old CMake versions.