fix: Support TOML up to v1.0.0-rc.1 spec.

[BradenM]

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Fixes #1836 🦕

This PR updates @iarna/toml the latest release of v3.0.0, which supports up to TOML v1.0.0-rc.1.

While it does not explicitly state support for v1.0.0, it is worth noting that all structrural changes were introduced in the rc.1 (namely, heterogeneous arrays).

For reference, you can see the test added in cf0a809 failing (w/o updating the lib) here:
https://github.com/BradenM/release-please/actions/runs/4040572970/jobs/6946340169#step:8:5167

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[chingor13]

Thanks!