workflows/triage: skip for BrewTestBot PRs

[Rylan12]

• 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?
• Have you successfully run brew man locally and committed any changes?

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The triage workflow is supposed to skip PRs opened by @BrewTestBot. However, it does not which eventually causes problems because @BrewTestBot tries (and fails) to approve it's own PR. Seen in #9334.

Note: I haven't tested this PR

Based on the GitHub API documentation for getting the authenticated user, the user object that is retrieved contains an object with more metadata rather than just the username. To get the username, we can use user.login.

While I haven't tested this PR, I've done something similar in actions/stale#231. There, I also used github.users.getAuthenticated() and then accessed the user's login via .data.login. Also, lower down in the workflow file, another comparison is made between review.user.login and user.login to filter only @BrewTestBot reviews. From these, I'm reasonably confident in this change.

CC: @reitermarkus

[BrewTestBot]

Review period ended.