Update dependency flake8-isort to v3

This MR contains the following updates:

Package	Type	Update	Change
flake8-isort	dev-dependencies	major	^2.8.0 -> ^3.0.0

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Release Notes

gforcada/flake8-isort

v3.0.0

Compare Source

• Let isort search the configuration, rather than flake8-isort try to find it. [jnns]

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