chore(NODE-7450): remove script to sync specifications repo to driver repo

[seanrmilligan]

Description

Summary of Changes

Remove sync script used for updating the driver repo with new spec test files from the specification repo.

What is the motivation for this change?

• The script has not been used in years and only exists as a pitfall for new devs.
• The script's purpose will be superseded by NODE-7450

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

[Copilot]

Pull request overview

Removes a legacy maintenance script (etc/update-spec-tests.sh) that previously synced spec test fixtures from the mongodb/specifications repository into this driver, reducing the chance of accidental or outdated workflows being used.

Changes:

• Deleted etc/update-spec-tests.sh, the script used to fetch and rsync spec tests into test/spec/.

[nbbeeken]

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