Remove panasonic_viera from discovery documentation

[frenck]

Proposed change

Reported in home-assistant/core#45073 that it was impossible to ignore panasonic_viera, which is correct, as it has been removed in:

home-assistant/core#34909

This PR correct the documentation to reflect that.

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 logo's and icons in Brands repository.
• 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:
• Link to parent pull request in the Brands repository:
• This PR fixes or closes issue: fixes Cannot ignore panasonic_viera in discovery component core#45073

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]

LOL duplicate of #16167, which was just opened as well.