[Docs] Filter website-only issues from changelogs

[asfimport]

The "Website" component is used to identify issues requiring changes to the Arrow website. These changes are made independent of Arrow releases, rendering the fixVersion field pointless. Existing tools and procedures continue to populate this field, though, and resulting in website-only changes being included in version-specific release notes months later. By way of example, the 8.0.0 release notes include:

• ARROW-14776 - [Website] Don’t include squashed commits in merge commit message

• ARROW-15472 - [Website] Add Flight SQL blog post

• ARROW-15491 - [Website] Rotate PMC chair for 2022

• ARROW-15902 - [Website] Add new committers: Raphael Taylor-Davies, Wang Xudong, Yijie Shen, Kun Liu

• ARROW-15931 - [Website] Add explicit Apache LICENSE.txt and NOTICE.txt files to apache/arrow-site repository

• ARROW-15683 - [Website][Rust][DataFusion] Make a 7.0.0 release announcement blog

• ARROW-16411 - [Website] Migrate to Matomo from Google Analitics

  The fixVersion should not be populated with an Arrow release version for website-only changes. It could be left blank, or a website-only version value could be created.

Reporter: Todd Farmer / @toddfarmer

_{Note: This issue was originally created as ARROW-17244. Please see the migration documentation for further details.}

[github-actions]

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