[SPARK-53653][DOC] Update rexml gem version to 3.4.4

[bjornjorgensen]

What changes were proposed in this pull request?

Update rexml from version 3.3.9 to rexml 3.4.4

Why are the changes needed?

CVE-2025-58767
There are also some fixes in the 2 last versions.
https://github.com/ruby/rexml/releases

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Installed ruby-dev and pip installed mkdocs and run SKIP_API=1 bundle exec jekyll build

Configuration file: /home/bjorn/github/spark/docs/_config.yml

************************
* Building error docs. *
************************
Generated: docs/_generated/error-conditions.html
            Source: /home/bjorn/github/spark/docs
       Destination: /home/bjorn/github/spark/docs/_site
 Incremental build: disabled. Enable with --incremental
      Generating... 
Warning: Tolerating missing API files because the following skip flags are set: SKIP_API
                    done in 4.27 seconds.
 Auto-regeneration: disabled. Use --watch to enable.

Was this patch authored or co-authored using generative AI tooling?

No.

[bjornjorgensen]

I have also updated spark-website apache/spark-website#635