Update rack gem to version 2.2.3.1

What does this MR do and why?

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/363882

This updates rack to fix recently disclosed CVEs

• https://groups.google.com/g/ruby-security-ann/c/L2Axto442qk
• https://groups.google.com/g/ruby-security-ann/c/LWB10kWzag8

Diff: https://my.diffend.io/gems/rack/2.2.3/2.2.3.1

Screenshots or screen recordings

N/A

How to set up and validate locally

No specific testing I can think of, other than checking that tests are green and the application works in general.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.