Fix Hue grouped light color_mode calculation

[marcelveldt]

Proposed change

Fixes a small typo in the color mode calculation for Hue light groups.
If the group contains brightness-only bulbs, the color mode would still report color_temp.

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 #
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[probot-home-assistant]

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