GH-46688: [Ruby] Fix a typo

[kou]

Rationale for this change

There is a typo.

FYI: This is not a critical because this typo exists in code that is only executed in an error case.

What changes are included in this PR?

Fix a typo.

Are these changes tested?

Yes.

Are there any user-facing changes?

Yes.

• GitHub Issue: [Ruby] extconf.rb:59:in <main>': undefined local variable or method version' for main:Object (NameError) #46688

[github-actions]

⚠️ GitHub issue #46688 has been automatically assigned in GitHub to PR creator.

[hiroyuki-sato]

+1 (I can't test on my local machine yet.)

[amoeba]

+1

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 4 benchmarking runs that have been run so far on merge-commit b119f5e.

There were 81 benchmark results with an error:

• Commit Run on amd64-m5-4xlarge-linux at 2025-06-04 00:16:26Z
  • tpch (R) with engine=arrow, format=parquet, language=R, memory_map=False, query_id=TPCH-05, scale_factor=10
  • tpch (R) with engine=arrow, format=parquet, language=R, memory_map=False, query_id=TPCH-07, scale_factor=10
• and 79 more (see the report linked below)

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 4 possible false positives for unstable benchmarks that are known to sometimes produce them.