chore(deps): bump nox-poetry from 0.8.4 to 0.8.5 in /.github/workflows

Bumps [nox-poetry](/~https://github.com/cjolowicz/nox-poetry) from 0.8.4 to 0.8.5.
- [Release notes](/~https://github.com/cjolowicz/nox-poetry/releases)
- [Commits](cjolowicz/nox-poetry@v0.8.4...v0.8.5)

Includes a manual change to remove a `# type: ignore[...]` on an
attribute that now *is* typed by `nox-poetry` in `noxfile.py`, see
/~https://github.com/NicolasT/gptsum/pull/60/checks?check_run_id=2473759883#step:7:18.

Signed-off-by: dependabot[bot] <support@github.com>
Signed-off-by: Nicolas Trangez <ikke@nicolast.be>

.github/workflows/constraints.txt

@@ -1,5 +1,5 @@
 pip==21.1
 nox==2020.12.31
-nox-poetry==0.8.4
+nox-poetry==0.8.5
 poetry==1.1.6
 virtualenv==20.4.4

noxfile.py

@@ -97,7 +97,7 @@ def tests(session: Session) -> None:
 def coverage(session: Session) -> None:
     """Produce the coverage report."""
     # Do not use session.posargs unless this is the only session.
-    nsessions = len(session._runner.manifest)  # type: ignore[attr-defined]
+    nsessions = len(session._runner.manifest)
     has_args = session.posargs and nsessions == 1
     args = session.posargs if has_args else ["report"]