Enable the PRESET_MODE FanEntityFeature for VeSync air purifiers

[DuckyCrayfish]

Proposed change

This change enables the PRESET_MODE FanEntityFeature on all VeSync air purifiers, as the functionality already existed, but the feature flag was not enabled.

As a result, the entity detail page will now list presets modes like "sleep" and "auto" when applicable.

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)
• Deprecation (breaking change to happen in the future)
• 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:

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[home-assistant]

Hey there @markperdue, @webdjoe, @TheGardenMonkey, mind taking a look at this pull request as it has been labeled with an integration (vesync) you are listed as a code owner for? Thanks!

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[edenhaus]

Thanks @DuckyCrayfish 👍

I changed it to be a bugfix as only the supported feature was missing.