docs/Common-Issues-for-Core-Contributors: add steps to fix failed bottle publish

[Moisan]

Based on @jonchang comments on the Homebrew maintainers slack channel. I put this issue at the top since I think it happens more often than the ld internal error.

• 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 tests with your changes locally?

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[jonchang]

Thanks for taking the initiative on this! Just a few suggestions here.

[Bo98]

I'd add

• git reset --hard origin/master to return to the latest commit and discard the commits made by brew pr-pull.

as the third step.

Changes addressed

[MikeMcQuaid]

Thanks @Moisan and all!