Remove documentation related to deprecated state attributes

[tr4nt0r]

Proposed change

Remove section related to extra state attributes will get deprecated in the parent-PR

(not sure when to remove documentation, when the features get deprecated or after the 6 months grace period when the feature is removed)

Type of change

• [ ] Spelling, grammar or other readability improvements (current branch).
• [ ] Adjusted missing or incorrect information in the current documentation (current branch).
• [ ] Added documentation for a new integration I'm adding to Home Assistant (next branch).
  • [ ] I've opened up a PR to add logos and icons in Brands repository.
• [ ] Added documentation for a new feature I'm adding to Home Assistant (next branch).
• [x] Removed stale or deprecated documentation.

Additional information

• Link to parent pull request in the codebase: https://github.com/home-assistant/core/pull/128126
• Link to parent pull request in the Brands repository:
• This PR fixes or closes issue: fixes #

Checklist

• [x] This PR uses the correct branch, based on one of the following:
  • I made a change to the existing documentation and used the current branch.
  • I made a change that is related to an upcoming version of Home Assistant and used the next branch.
• [x] The documentation follows the Home Assistant documentation standards.

Summary by CodeRabbit

• Documentation
  • Enhanced descriptions for Habitica integration functionalities, including sensors, to-do lists, and button controls.
  • Expanded details on specific attributes like "Gems" and "Mystic hourglasses."
  • Clarified task management capabilities, including adding, deleting, and editing tasks.
  • Elaborated on button actions and their effects on character status in Habitica.
  • Refined API service section with structured explanations and examples for user-specific actions.