Upgrade modver to v2.9.0

[bobg]

This PR upgrades Modver to v2.9.0, needed in order to properly check PRs (such as #18) originating from forked copies of the repository. See https://github.com/bobg/modver/releases/tag/v2.8.0.

[github-actions]

Modver result

This report was generated by Modver,
a Go package and command that helps you obey semantic versioning rules in your Go module.

This PR requires (at least) an increase in your module's patchlevel.

checking keyedSorter
  old and new versions of github.com/bobg/go-generics/v3/slices.keyedSorter[S ~[]T, T any] are not identical
    Patchlevel

[coveralls]

Pull Request Test Coverage Report for Build 10228536153

Details

• 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 87.854%

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Totals
Change from base Build 10190897285:	0.0%
Covered Lines:	1056
Relevant Lines:	1202

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💛 - Coveralls