chore: drop stale EOLRails brakeman ignoresince Rails 8.1 upgrade landed

[samuel-sarmah]

What github issue is this PR for, if any?

Resolves #7143

What changed, and why?

• Removes one entry from config/brakeman.ignore: the EOLRails (warning_code: 122, "Unmaintained dependency") suppression for "Support for Rails 8.0.5.1 ends on 2026-10-07".
• No other ignore entries are touched, the Dynamic Render Path suppression for StaticController#page stays

How is this tested? (please write rspec and jest tests!) 💖💪

Note: if you see a flake in your test build in github actions, please post in slack #casa "Flaky test: " :) 💪
Note: We love capybara tests! If you are writing both haml/js and ruby, please try to test your work with tests at every level including system tests like https://github.com/rubyforgood/casa/tree/main/spec/system

• Removed the EOLRails entry from config/brakeman.ignore.
• Ran bundle exec brakeman and confirmed it passes with the entry gone.

Screenshots please :)

Not available, not a user-facing issue

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