pytest-flake8 is breaking CI, so remove it

support/setup_ci.sh

@@ -30,10 +30,4 @@ conda create --yes -q -n python${python_version} -c salilab python=${python_vers
 eval "$(conda shell.bash hook)"
 conda activate python${python_version}
 
-if [ ${python_version} = "2.7" ]; then
-  # pytest-flake8 1.1.0 tries to import contextlib.redirect_stdout, which
-  # isn't present in Python 2
-  pip install pytest-cov coverage 'pytest-flake8<1.1'
-else
-  pip install pytest-cov coverage pytest-flake8
-fi
+pip install pytest-cov coverage