Correct dependency on puffin to 0.19.1, preventing a possible build failure.

[kpreid]

What

re_tracing::profile_function_if uses puffin::profile_function_if, which only exists in puffin 0.19.1 and not 0.19.0. This incorrect version would cause a compilation failure for users updating to Rerun 0.18 who already have puffin 0.19.0 in their lock file.

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
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• If have noted any breaking changes to the log API in CHANGELOG.md and the migration guide

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