Support Rack 3.x

[YOU54F]

Support for Rack 2.x and 3.x was added in

https://github.com/pact-foundation/pact-mock_service/pull/152

and released in 3.12.2

https://rubygems.org/gems/pact-mock_service/versions/3.12.2

This is now preventing upgrades to

pact-ruby-standalone

Fetching gem metadata from http://rubygems.org/............
Resolving dependencies...
Could not find compatible versions

Because pact-mock_service >= 3.12.2 depends on rack >= 3.0, < 4.0
  and pact-provider-verifier >= 1.26.0 depends on rack ~> 2.1,
pact-mock_service >= 3.12.2 is incompatible with pact-provider-verifier >=
1.26.0.
So, because Gemfile depends on pact-mock_service = 3.12.2
  and Gemfile depends on pact-provider-verifier = 1.38.0,
  version solving has failed.

pact-ruby-cli

bundle update pact-mock_service
A gemspec development dependency (bump, ~> 0.9) is being overridden by a Gemfile dependency (bump, ~> 0.5).
This behaviour may change in the future. Please remove either of them, or make sure they both have the same requirement
Fetching gem metadata from https://rubygems.org/...........
Resolving dependencies...
Resolving dependencies...
Bundler attempted to update pact-mock_service but its version stayed the same
Bundle updated!