chore(deps): update syn requirement from 2 to 3

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Updates the requirements on syn to permit the latest version.

Release notes

Sourced from syn's releases.

3.0.3

• Documentation improvements

Commits

• 23dbaab Release 3.0.3
• 16aad4e Merge pull request #2071 from dtolnay/compatibility
• 42181b8 Add explanation of compatibility strategy
• f3af08e Update test suite to nightly-2026-07-21
• 88ee7be Release 3.0.2
• 587bc20 Merge pull request #2070 from dtolnay/emptyrange
• 96801f7 Allow Error::new_range at empty cursor range
• 9dc16c9 Merge pull request #2069 from dtolnay/prevspan
• 1db76b7 Align on using impl trait across all Error constructors
• bfa1ebf Make Cursor::prev_span public
• Additional commits viewable in compare view

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[jackmoxley]

Already applied — main carries syn = { version = "3", features = ["full"] } as of #47, so this diff is now a no-op.

Raised at 15:17, in the window between #46 and #47 merging.

Worth noting this arrived as a single PR rather than the duplicate pair (#40 + #41) seen before — #46 removed the redundant /macros cargo entry from .github/dependabot.yml, which was the cause of the double-raise.

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OK, I won't notify you again about this release, but will get in touch when a new version is available. If you'd rather skip all updates until the next major or minor version, let me know by commenting @dependabot ignore this major version or @dependabot ignore this minor version. You can also ignore all major, minor, or patch releases for a dependency by adding an ignore condition with the desired update_types to your config file.

If you change your mind, just re-open this PR and I'll resolve any conflicts on it.