Bump nox-poetry from 0.5.0 to 0.8.4 in /.github/workflows

Bumps [nox-poetry](https://github.com/cjolowicz/nox-poetry) from 0.5.0 to 0.8.4.
- [Release notes](https://github.com/cjolowicz/nox-poetry/releases)
- [Commits](cjolowicz/nox-poetry@v0.5.0...v0.8.4)

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/constraints.txt

@@ -1,5 +1,5 @@
 pip==21.0.1
 nox==2020.8.22
-nox-poetry==0.5.0
+nox-poetry==0.8.4
 poetry==1.1.4
 virtualenv==20.1.0