Update rack gem (major)

Context

!112453 (closed) was opened by @gitlab-dependency-update-bot, but it contains three major upgrades for three separate gems.

We are splitting this work into three separate issues.

Goal

Upgrade rack to version 3.x.

Package	Update	Change
rack	major	'~> 2.2.6', '>= 2.2.6.3' -> '~> 3.0.4', '>= 3.0.4.2'

Technical notes for the upgrade

See !112453 (comment 1286482097)

Dependencies that need to be updated

• sidekiq !138882 (merged)
• redis-actionpack !140468 (merged)
• pact !140478 (merged)
• grape !140556 (merged)
• sprockets #373997
• rails !124004 (closed)