PYTHON-5327 Add test for SRV hostname validation

[aclark4life]

PYTHON-5327

Changes in this PR

Test Plan

Checklist

Checklist for Author

• Did you update the changelog (if necessary)?
• Is there test coverage?
• Is any followup work tracked in a JIRA ticket? If so, add link(s).

Checklist for Reviewer

• Does the title of the PR reference a JIRA Ticket?
• Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
• Is all relevant documentation (README or docstring) updated?

[evergreen-ci-prod]

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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