Update slackapi/slack-github-action action to v1.27.1 #902

Job	Run time
black	19s
bandit	22s
flake8	19s
mypy	36s
pydocstyle	19s
yamllint	24s
pylint	47s
unittest (3.8, 2.x)	1m 40s
unittest (3.9, 2.x)	37s
unittest (3.10, 2.x)	1m 39s
unittest (3.11, 2.x)	1m 41s
unittest (3.11, 1.x)	38s
Publish to GitHub	1s
Push Package to PyPI	1s
Send notification to the Slack	1s
	9m 24s

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