Update Rack gem to latest 3.0.x

[aduth]

🛠 Summary of changes

Updates the Rack gem to the latest version.

Changelog: https://github.com/rack/rack/blob/main/CHANGELOG.md

Note that the 3.1.0 release includes a number of breaking changes, though upon review, there does not appear to be any changes impacting our current usage. Edit: After incompatibilities observed, the changes now upgrade to the latest security release in the 3.0.x line instead.

📜 Testing Plan

Verify build passes.

Verify make audit produces no security advisories output after running bundle install.

[solipet]

Looks like a simple enough change, but somehow it is breaking tons (all?) of the feature specs!

[aduth]

Yeah, there seems to be some incompatibility with capybara-webmock or webmock. I'm digging into it, but may end up going back to the (patched) 3.0.x if it doesn't pan out.

[aduth]

The underlying issue seems to be with capybara-webmock gem using an outdated reference to Rack::Handler, which was extracted to a separate gem in Rack 3. Unclear why this works in 3.0.x and not 3.1.x. (Edit: Likely related to rack/rack@fd7e0ad)

There's a related pull request at hashrocket/capybara-webmock#56

In the meantime, in 8b2f93f I've downgraded to the version on the 3.0.x line with the patch.