Minor: fix local clippy using anon deprecated tonic-build API

[alamb]

Which issue does this PR close?

Closes #.

Rationale for this change

When I run clippy locally I seeing the following error:

error: use of deprecated method `tonic_build::Builder::compile_with_config`: renamed to `compile_protos_with_config()`
  --> arrow-flight/gen/src/main.rs:32:10
   |
32 |         .compile_with_config(prost_config(), &[proto_path], &[proto_dir])?;
   |          ^^^^^^^^^^^^^^^^^^^
   |
   = note: `-D deprecated` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(deprecated)]`

What changes are included in this PR?

Change the code to use the non deprecated API

Are there any user-facing changes?

No, this is an internal build script

[etseidl]

Confirm I can run clippy now too. Thanks for this!

[alamb]

Thanks @etseidl for the review