Bump flux_led to 0.28.20

[bdraco]

Proposed change

• Fixes various bad assumptions about the protocol used for the 0x1A devices

Changelog: lightinglibs/flux_led@0.28.17...0.28.20

fixes lightinglibs/flux_led#147

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 Support for Christmas lights 0x1A / 0x10 (aka 6 LED Fairylights) lightinglibs/flux_led#147
• This PR is related to issue:
• Link to documentation pull request:

Checklist

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[probot-home-assistant]

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