Upgrade isort to 5.9.3

[frenck]

Proposed change

Upgrades isort to 5.9.3

Release notes:

• https://github.com/PyCQA/isort/blob/main/CHANGELOG.md#590-june-21st-2021
• https://github.com/PyCQA/isort/blob/main/CHANGELOG.md#591-june-21st-2021-hotfix
• https://github.com/PyCQA/isort/blob/main/CHANGELOG.md#592-july-8th-2021
• https://github.com/PyCQA/isort/blob/main/CHANGELOG.md#593-july-28-2021

Git compare view: PyCQA/isort@5.9.0...5.9.3

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

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• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

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