feat(NODE-7159)!: remove Kerberos export

[baileympearson]

Description

Summary of Changes

This PR removes the named Kerberos export.

Notes for Reviewers

What is the motivation for this change?

Release Highlight

Kerberos no longer exported from the package

The kerberos package exported an undocumented named export, Kerberos, which was used for compatibility with unsupported (<4.x) MongoDB drivers. This export has been removed.

If you are relying on this export, simply import from the kerberos package directly. ex:

// before
const initializeClient = require('kerberos').Kerberos.initializeClient;

// after
const initializeClient = require('kerberos').initializeClient;

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