PYTHON-6157 Bundle libmongocrypt 1.20.5

[aclark4life]

https://jira.mongodb.org/browse/PYTHON-6157

Changes in this PR

Bump the bundled libmongocrypt in pymongocrypt release wheels from 1.20.4 to 1.20.5.

Test Plan

• No code changes. The 1.20.5 release artifacts exist and are verified by release.sh at wheel build time.
• Evergreen patch build.

Checklist

Checklist for Author

• Did you update the changelog (if necessary)?
• Is the intention of the code captured in relevant tests?
• If there are new TODOs, has a related JIRA ticket been created?

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?)
• Have you checked for spelling & grammar errors?
• Is all relevant documentation (README or docstring) updated?