build(deps): update syn requirement from 1.0.8 to 2.0.28

[dependabot[bot]]

Updates the requirements on syn to permit the latest version.

Release notes

Sourced from syn's releases.

2.0.28

• Fix inconsistency between full and non-full expression parse errors (#1491)

Commits

• 44c5fdd Release 2.0.28
• 65aa662 Merge pull request #1491 from dtolnay/expectedexpr
• 91c84f6 Fix trivial difference between full and non-full expression parse errors
• f79ba15 Update test suite to nightly-2023-07-29
• 41c3847 Update test suite to nightly-2023-07-27
• a171121 Release syn-codegen 0.4.1
• dd250f4 Also add --generate-link-to-definition for syn-codegen
• bb23493 Release 2.0.27
• e3a15a9 Opt in to generate-link-to-definition when building on docs.rs
• 36a743a Merge pull request #1490 from dtolnay/docinline
• Additional commits viewable in compare view

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[coveralls]

Pull Request Test Coverage Report for Build 5716204945

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 57.06%

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Totals
Change from base Build 5682232138:	0.0%
Covered Lines:	2865
Relevant Lines:	5021

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💛 - Coveralls

[dependabot[bot]]

Superseded by #91.