upgrade pytest to fix running tests locally

[chdsbd]

I did poetry update pytest

Before this change I was getting this error:

___________________________________________________________ ERROR collecting kodiak/tests/event_handlers/test_check_run.py ____________________________________________________________
.venv/lib/python3.7/site-packages/_pytest/python.py:618: in _importtestmodule
    mod = import_path(self.path, mode=importmode, root=self.config.rootpath)
.venv/lib/python3.7/site-packages/_pytest/pathlib.py:533: in import_path
    importlib.import_module(module_name)
../../../.pyenv/versions/3.7.13/lib/python3.7/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
<frozen importlib._bootstrap>:1006: in _gcd_import
    ???
<frozen importlib._bootstrap>:983: in _find_and_load
    ???
<frozen importlib._bootstrap>:967: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:677: in _load_unlocked
    ???
.venv/lib/python3.7/site-packages/_pytest/assertion/rewrite.py:168: in exec_module
    exec(co, module.__dict__)
kodiak/tests/event_handlers/test_check_run.py:11: in <module>
    from kodiak.queue import WebhookEvent, check_run
kodiak/queue.py:30: in <module>
    from kodiak.pull_request import evaluate_pr
kodiak/pull_request.py:17: in <module>
    from kodiak.evaluation import mergeable
kodiak/evaluation.py:11: in <module>
    import rure as re
.venv/lib/python3.7/site-packages/rure/__init__.py:3: in <module>
    from rure.lib import Rure, RureSet
E     File "/Users/christopherdignam/projects/kodiak/bot/.venv/lib/python3.7/site-packages/rure/lib.py", line 50
E       """
E        ^
E   SyntaxError: invalid escape sequence \A