fix: remove deprecated --exclude-mail flag from lychee config [FaaFyfxR9WAQrL7FcAgEHJvztd8cVMxvjHRS55rw1nwH]

[waterWang]

Fixes #8077

The --exclude-mail flag was removed in a newer version of lychee, causing the link checker to fail with "unexpected argument '--exclude-mail' found" on every run since July 22. Mail links are skipped by default now, so the flag is no longer needed.

This is a one-line fix: simply remove the --exclude-mail argument from the lychee args.

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[Scottcjn]

Verified and this is correct.

Current lychee has no --exclude-mail option. lychee-bin/src/config/mod.rs only defines include_mail, which returns self.include_mail.unwrap_or(false), and the filter is uri.is_mail() && !self.include_mail. There are upstream tests literally named test_exclude_mail_by_default. So mail links are skipped by default and the flag that used to request that is gone.

That means the removal is behaviour-preserving as well as necessary: nothing starts getting checked that was not being checked before.

Single line, single purpose, no test impact. Looks good to me.

One scheduling note: #8082 also deletes this same line as part of an unrelated docs change, so the two conflict in .github/workflows/lychee.yml. I would land this one first and let #8082 rebase, since this is the change that is actually about the flag.