Lock to rack-cors 2.0.0 to avoid problem with rack-cors 2.0.1

[charleyf]

🛠 Summary of changes

Right now all lint tasks are failing in main because there's a newly reported file permission vulnerability in rack-cors (link) version 2.0.1 (latest). This PR addresses that by locking our version to 2.0.0, the latest version of rack-cors without this vulnerability (link).

Presumably we'll be able to use 2.0.1 again once they've patched the problem.

The error:

--- bundler-audit ---
bundle exec bundler-audit check --update
Updating ruby-advisory-db ...
From https://github.com/rubysec/ruby-advisory-db
 * branch            master     -> FETCH_HEAD
Already up to date.
Updated ruby-advisory-db
ruby-advisory-db:
  advisories:   875 advisories
  last updated: 2024-02-27 14:25:50 -0800
  commit:       1c7d5b5233d4c1ace4b6141bb949a2d54028d18e
Name: rack-cors
Version: 2.0.1
CVE: CVE-2024-27456
GHSA: GHSA-785g-282q-pwvx
Criticality: Unknown
URL: https://github.com/advisories/GHSA-785g-282q-pwvx
Title: Rack CORS Middleware has Insecure File Permissions
Solution: remove or disable this gem until a patch is available!

Vulnerabilities found!
make: *** [lint] Error 1

📜 Testing Plan

• Run make lint in main notice the failure.
• Run make lint in this branch, the failure is gone.