docs/New-Maintainer-Checklist.md: remove automated steps

[nandahkrishna]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?

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This PR removes steps in the New Maintainer Checklist that have been automated (adding new maintainers to the README and running brew man, updating PLC members).

[BrewTestBot]

Review period will end on 2021-03-02 at 00:00:00 UTC.

[issyl0]

Thanks, Nanda! 🌟

[MikeMcQuaid]

Thanks @nandahkrishna!

[BrewTestBot]

Review period ended.