Update syn requirement from 2.0.0 to 3.0.3

[dependabot]

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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[CryZe]

@copilot Can you fix the code?

error[E0599]: no method named is_some found for enum PointerMutability in the current scope
2026-07-22T07:56:27.1642566Z --> capi/bind_gen/src/main.rs:101:41
2026-07-22T07:56:27.1642919Z |
2026-07-22T07:56:27.1643267Z 101 | ty.kind = if ptr.mutability.is_some() {
2026-07-22T07:56:27.1643747Z | ^^^^^^^ method not found in PointerMutability

[Copilot]

@copilot Can you fix the code?

error[E0599]: no method named is_some found for enum PointerMutability in the current scope...

Fixed in the latest commit. In syn 3.x, TypePtr::mutability changed from Option<Token![mut]> to a PointerMutability enum with Const and Mut variants, so is_some() no longer applies. Replaced with matches!(ptr.mutability, syn::PointerMutability::Mut(_)).