arrow

GH-44885: [Dev][Release] Update test condition in utils-prepare.sh (#44862)

### Rationale for this change

The `update_versions` function in `dev/release/utils-prepare.sh` is called by `dev/release/post-12-bump-versions.sh` and one of the tasks it performs is to update `c_glib/generate-version-header.py` with new major versions. There was a bug in `update_versions` that incorrectly updated this file on minor releases, leading to duplicate major versions being listed. This change fixes that.

### What changes are included in this PR?

Fixed version of `update_versions` in `dev/release/utils-prepare.sh`.

### Are these changes tested?

Yes, locally.

### Are there any user-facing changes?

No.

Closes https://github.com/apache/arrow/issues/44885
* GitHub Issue: #44885

Lead-authored-by: Sutou Kouhei <kou@clear-code.com>
Co-authored-by: Bryce Mecum <petridish@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>