feat(NODE-7139): remove pre-4.2 logic and deprecate dead code

[dariakp]

Description

Summary of Changes

This PR removes the remaining unreachable code given our min supported wire version is 8. It also deprecates ServerCapabilities and ReadPreference.minWireVersion, which are publicly exposed but serve no real function in our current code base.

Notes for Reviewers

ReadPreference.minWireVersion was only ever set to 5, hence removing the corresponding commonWireVersion check in server selection is safe.

What is the motivation for this change?

NODE-7139

Release Highlight

ServerCapabilities and ReadPreference.minWireVersion are deprecated

Neither the ServerCapabilities class nor the ReadPreference.minWireVersion property were ever intended for public use and, internally, are effectively dead code with the driver's minimum supported server version being 4.2.

Double check the following

• Lint is passing (npm run check:lint)
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket

[durran]

Love PRs with all removals.