Update flat buffers version from 1.9 to 1.12

[jvictorhuguenin]

Remove dependency of Dremio on a flatc binary during arrow build, and update flat buffers version to 1.12. In the current version, Arrow doesn't need a flatc binary during any phase of building as explained in this PR: https://github.com/apache/arrow/pull/10058 Currently, it isn't possible to update Dremio's arrow version to 5.0.0, because on any test execution using any arrow dependency it can't find some classes only found on flatc artifact, which arrow doesn't have anymore.

Also updates the version of flat buffers for 1.12, to keep it aligned with the Arrow version.