brew uninstall respects the HOMEBREW_NO_INSTALL_FROM_API env var

[wheelerlaw]

• 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 lgtm (style, typechecking and tests) with your changes locally?

---

This PR changes brew uninstall to respect the HOMEBREW_NO_INSTALL_FROM_API env var. This resolves this discussion I opened.

[MikeMcQuaid]

Thanks!