workflows/tests: remove duplicate step

[carlocab]

• 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 is already done in the formula-audit job:

brew/.github/workflows/tests.yml

Lines 157 to 158 in de1c4e2

	- name: Generate formula API
	run: brew generate-formula-api --dry-run

[carlocab]

Ah, no, I see. This step runs on macOS, but the other one runs on Linux. Do we really need both?

[MikeMcQuaid]

@carlocab Yes. This was added by when we had formulae generation failing on one platform but not another.