[Snyk] Fix for 1 vulnerabilities - Examples(Zoo App) - Rack 3.x

[mefellows]

This PR was automatically created by Snyk using the credentials of a real user.

Snyk has created this PR to fix one or more vulnerable packages in the `rubygems` dependencies of this project.

Changes included in this PR

• Changes to the following files to upgrade the vulnerable dependencies to a fixed version:
  • example/zoo-app/Gemfile

⚠️ Warning

Failed to update the Gemfile.lock, please update manually before merging.

Vulnerabilities that will be fixed

With an upgrade:

Severity	Priority Score (*)	Issue	Breaking Change	Exploit Maturity
	616/1000 Why? Proof of Concept exploit, Has a fix available, CVSS 5.9	Web Cache Poisoning SNYK-RUBY-RACK-1061917	Yes	Proof of Concept

(*) Note that the real score may have changed since the PR was raised.

Check the changes in this PR to ensure they won't cause issues with your project.

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[YOU54F]

Stopped from moving to Rack 3.x due to pin in pact-mock_service

Bundler could not find compatible versions for gem "rack":
  In Gemfile:
    rack (~> 3.0, >= 3.0.0)

    pact was resolved to 1.63.0, which depends on
      pact-mock_service (~> 3.0, >= 3.3.1) was resolved to 3.11.0, which depends on
        rack (~> 2.0)

[YOU54F]

Fixed in #308