Clarify the version of wiremock for the new helpers released in 3.6.0

[leeturner]

This PR clarifies the version of WireMock needed for the helpers released in WireMock 3.6.0 to avoid confusion for people using older versions.

References

• https://wiremock-community.slack.com/archives/C03N1E6HFPY/p1718184639235809

Submitter checklist

• [x] The PR request is well described and justified, including the body and the references
• [x] The PR title represents the desired changelog entry
• [x] If the change against WireMock 2 functionality (incompatible with WireMock 3), it is submitted against the 2.x branch
• [x] The repository's code style is followed (see the contributing guide)

Details: Contributor Guide