[Snyk] Fix for 7 vulnerabilities

[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 :-------------------------:|-------------------------|:-------------------------|:-------------------------|:-------------------------  | **646/1000**
**Why?** Proof of Concept exploit, Has a fix available, CVSS 6.5 | External Control of Assumed-Immutable Web Parameter
[SNYK-RUBY-HTTPARTY-3188560](https://snyk.io/vuln/SNYK-RUBY-HTTPARTY-3188560) | No | Proof of Concept  | **616/1000**
**Why?** Proof of Concept exploit, Has a fix available, CVSS 5.9 | Web Cache Poisoning
[SNYK-RUBY-RACK-1061917](https://snyk.io/vuln/SNYK-RUBY-RACK-1061917) | Yes | Proof of Concept  | **479/1000**
**Why?** Has a fix available, CVSS 5.3 | Regular Expression Denial of Service (ReDoS)
[SNYK-RUBY-RACK-3237233](https://snyk.io/vuln/SNYK-RUBY-RACK-3237233) | No | No Known Exploit  | **479/1000**
**Why?** Has a fix available, CVSS 5.3 | Regular Expression Denial of Service (ReDoS)
[SNYK-RUBY-RACK-3237237](https://snyk.io/vuln/SNYK-RUBY-RACK-3237237) | No | No Known Exploit  | **479/1000**
**Why?** Has a fix available, CVSS 5.3 | Regular Expression Denial of Service (ReDoS)
[SNYK-RUBY-RACK-3237240](https://snyk.io/vuln/SNYK-RUBY-RACK-3237240) | No | No Known Exploit  | **589/1000**
**Why?** Has a fix available, CVSS 7.5 | Denial of Service (DoS)
[SNYK-RUBY-RACK-3356639](https://snyk.io/vuln/SNYK-RUBY-RACK-3356639) | No | No Known Exploit  | **551/1000**
**Why?** Recently disclosed, Has a fix available, CVSS 5.3 | Regular Expression Denial of Service (ReDoS)
[SNYK-RUBY-RACK-3360233](https://snyk.io/vuln/SNYK-RUBY-RACK-3360233) | No | No Known Exploit (*) 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. ------------ **Note:** *You are seeing this because you or someone else with access to this repository has authorized Snyk to open fix PRs.* For more information: 🧐 [View latest project report](https://app.snyk.io/org/pact-foundation-808/project/b6444bbf-90d0-4f04-9fa5-50a7fa41d790?utm_source=github&utm_medium=referral&page=fix-pr) 🛠 [Adjust project settings](https://app.snyk.io/org/pact-foundation-808/project/b6444bbf-90d0-4f04-9fa5-50a7fa41d790?utm_source=github&utm_medium=referral&page=fix-pr/settings) 📚 [Read more about Snyk's upgrade and patch logic](https://support.snyk.io/hc/en-us/articles/360003891078-Snyk-patches-to-fix-vulnerabilities) [//]: # (snyk:metadata:{"prId":"7450b59d-46de-421a-977e-e26b13e91628","prPublicId":"7450b59d-46de-421a-977e-e26b13e91628","dependencies":[{"name":"httparty","from":"0.20.0","to":"0.21.0"},{"name":"pact","from":"1.62.0","to":"1.63.0"},{"name":"pact_broker-client","from":"1.51.1","to":"1.51.1"},{"name":"rack","from":"2.2.4","to":"3.0.0"}],"packageManager":"rubygems","projectPublicId":"b6444bbf-90d0-4f04-9fa5-50a7fa41d790","projectUrl":"https://app.snyk.io/org/pact-foundation-808/project/b6444bbf-90d0-4f04-9fa5-50a7fa41d790?utm_source=github&utm_medium=referral&page=fix-pr","type":"auto","patch":[],"vulns":["SNYK-RUBY-HTTPARTY-3188560","SNYK-RUBY-RACK-1061917","SNYK-RUBY-RACK-3237233","SNYK-RUBY-RACK-3237237","SNYK-RUBY-RACK-3237240","SNYK-RUBY-RACK-3356639","SNYK-RUBY-RACK-3360233"],"upgrade":["SNYK-RUBY-HTTPARTY-3188560","SNYK-RUBY-RACK-1061917","SNYK-RUBY-RACK-3237233","SNYK-RUBY-RACK-3237237","SNYK-RUBY-RACK-3237240","SNYK-RUBY-RACK-3356639","SNYK-RUBY-RACK-3360233"],"isBreakingChange":true,"env":"prod","prType":"fix","templateVariants":["pr-warning-shown","priorityScore"],"priorityScoreList":[646,616,479,479,479,589,551],"remediationStrategy":"vuln"}) --- **Learn how to fix vulnerabilities with free interactive lessons:** 🦉 [Regular Expression Denial of Service (ReDoS)](https://learn.snyk.io/lessons/redos/javascript/?loc=fix-pr)

[YOU54F]

httparty pin is in master, rack upgrade to 3.x covered in #277