arrow

GH-37742: [Python] Enable Cython 3 (#37743)

### Rationale for this change

Enable Cython 3.

### What changes are included in this PR?

* Unpin Cython version in builds.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

Yes, pyarrow will build with cython 3 by default.
* Closes: #37742

Authored-by: Dane Pitkin <dane@voltrondata.com>
Signed-off-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>