workflows: use GITHUB_TOKEN when checking license

[jonchang]

• 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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This should avoid errors from rate limited API calls when using hosted runners.

[Bo98]

Hmm, if there's going to be potential API errors then maybe me relying on --fail-if-changed will be a bad idea. I guess we should have --success-if-changed or something.

[jonchang]

Ah, to be clear, it's not an API error, just rate limiting from not using an authenticated API call. See https://github.com/Homebrew/brew/runs/881647497?check_suite_focus=true#step:12:8 for what I mean.

[Bo98]

Sure, though I don't trust GitHub uptime.

[jonchang]

If GitHub is down we'd probably have problems in addition to the rate limited test 😅