bump-formula-pr: wrap release notes in <pre> tags

[bevanjkay]

• 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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Continuation of #14918 - wraps the release notes in <pre> tags to prevent relative GitHub issue links from tagging unrelated issues - Example: Homebrew/homebrew-core#125133

[BrewTestBot]

Review period will end on 2023-03-16 at 12:05:07 UTC.

[BrewTestBot]

Review period skipped due to critical label.

[MikeMcQuaid]

Thanks again @bevanjkay!