lint(py3): Ignore B308 (Don't use str) (#23342)

setup.cfg

@@ -12,10 +12,11 @@ markers =
 
 [flake8]
 # File filtering is taken care of in pre-commit.
-# TODO(joshuarli): B102 doesn't apply to Python 3. Could remove it from sentry-flake8 in a future release.
+# TODO(py3): B102 doesn't apply to Python 3. Should be removed from sentry-flake8 in a future release.
+# TODO(py3): B308 doesn't apply to python 3. Should be removed from sentry-flake8 in a future release
 # E203 false positive, see https://github.com/PyCQA/pycodestyle/issues/373
 # W605 false positive until python3.8: https://github.com/PyCQA/pycodestyle/issues/755
-ignore = B102,F999,E203,E501,E128,E124,E402,W503,W504,W605,E731,C901,B007,B306,B009,B010
+ignore = B102,F999,E203,E501,E128,E124,E402,W503,W504,W605,E731,C901,B007,B306,B009,B010,B308
 
 # XXX: E501 is ignored, which disables line length checking.
 # Currently, the black formatter doesn't wrap long strings: https://github.com/psf/black/issues/182#issuecomment-385325274