Remove invalid scan_interval from AirVisual

[frenck]

Proposed change

Removes an invalid configuration parameter from the AirVisual example documentation: scan_interval.

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).
• Added documentation for a new feature I'm adding to Home Assistant (next branch).
• Removed stale or deprecated documentation.

Additional information

• Link to parent pull request in the codebase:
• This PR fixes or closes issue: fixes AirVisual doesn't support scan_interval any longer core#33182

Checklist

• 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.
• The documentation follows the Home Assistant documentation standards.

[frenck]

@bachya Feel free to merge next time 😉

[bachya]

@frenck Will do, thanks!