swift: update urls

[samford]

• Have you followed the guidelines for contributing?
• Have you ensured that your commits follow the commit style guide?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

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swift.org now redirects to www.swift.org, so this PR modifies the homepage to avoid the redirection as well as other URLs in the formula (for the sake of consistency). This affects the test block, so I haven't labeled this as CI-syntax-only.

[carlocab]

Building Swift takes (IIRC) 6+ hours and needs the self-hosted Linux runner, which will probably be tied up for a while. This change can probably wait for a version bump, or at least until the PRs that need it are done. Those are at least: #89488, #88036, #88210, #89262 and maybe #89642.

[samford]

This change can probably wait for a version bump, or at least until the PRs that need it are done.

There's certainly no rush on these particular changes (they're just a nice-to-have rather than a need-to-have), so waiting for a version bump is fine. Do we want to leave this open (so it won't be forgotten) and cancel CI for now or should I simply close it?

[carlocab]

Do we want to leave this open (so it won't be forgotten) and cancel CI for now or should I simply close it?

Either is fine with me.

[carlocab]

Included in #88210.