Add pytest back to the blocklist

Summary:
I did a round of pruning the nondeterminism blocklist recently because having
too many packages in it makes the regression checks less powerful and also
makes it harder to stress-test potential determinism improvements.

But there's always a risk of pruning packages that are actually nondeterministic;
I think this is particularly possible because the full mypy primer CI job runs
massively in parallel, creating a ton of resource contention that a smaller
stress-test might not (plus CI machines are sometimes pretty wimpy).

I've been seeing periodic - although relatively rare - nondeterminism on pytest
so I think we need to add it back.

Reviewed By: rchen152

Differential Revision: D91730726

fbshipit-source-id: 0eb011cb859bd4ff9cda7d3b78562f5782e8cad5

Author: stroxler

.github/workflows/mypy_primer.yml

@@ -61,7 +61,7 @@ jobs:
             --new $GITHUB_SHA --old base_commit \
             --num-shards 10 --shard-index ${{ matrix.shard-index }} \
             --debug \
-            --project-selector '^(?!.*(python-attrs/attrs|scipy/scipy|scikit-learn/scikit-learn|pandas-dev/pandas|google/jax|apache/spark|spack/spack|sympy/sympy|PyCQA/flake8-pyi|Gobot1234/steam\.py|rotki/rotki|enthought/comtypes))' \
+            --project-selector '^(?!.*(python-attrs/attrs|scipy/scipy|scikit-learn/scikit-learn|pandas-dev/pandas|google/jax|apache/spark|spack/spack|sympy/sympy|PyCQA/flake8-pyi|Gobot1234/steam\.py|rotki/rotki|enthought/comtypes|pytest-dev/pytest))' \
             --type-checker pyrefly \
             --output concise \
             | tee diff_${{ matrix.shard-index }}.txt