Relax plugin scalac phase order

[jackkoenig]

It must run after the typer, but doesn't need to "run right after". The
stricter dependency conflicted with the semanticdb-typer.

h/t Øyvind for finding this bug https://groups.google.com/g/chisel-users/c/K_vuliudgLg/m/IYx-QPd4AQAJ

I locally verified that I could reproduce the bug and this fixes it. Unfortunately this is a pretty hard thing to test for (in this repo at least)

Contributor Checklist

• [NA] Did you add Scaladoc to every public function/method?
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Type of Improvement

• bug fix

API Impact

No change

Backend Code Generation Impact

No change

Desired Merge Strategy

• Squash

Release Notes

Relax plugin scalac phase order. This makes the plugin work with tools like Scala Metals.

Reviewer Checklist (only modified by reviewer)

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