Remove support for discontinued services (chirb.it and sassmeister.com)

[uzulla]

This PR removes support for two services that have been shut down and are no longer accessible:

• chirb.it (Chirbit) - Audio sharing service
• sassmeister.com (SassMeister) - Sass playground

Services Status Evidence

chirb.it (Chirbit)

• Status: Service down and inaccessible
• Evidence:
  • Multiple user reports since January 2023 (over 2 years ago)
  • Connection failures: "Failed to connect to chirb.it port 80"
  • Monitoring site: https://issitedownrightnow.com/status/chirbit.com
  • User reports indicate: "The url chirbit.com does not resolve and there is no access to the site"

sassmeister.com (SassMeister)

• Status: Service discontinued, project archived
• Evidence:
  • GitHub repository archived on November 8, 2023 (read-only)
  • Repository: https://github.com/jedfoster/SassMeister
  • DNS resolution failure: "Could not resolve host: sassmeister.com"

Changes Made

chirb.it removal:

• Removed oEmbed provider entry from src/resources/oembed.php
• Removed test case from tests/PagesTest.php
• Deleted test fixtures and cached responses

sassmeister.com removal:

• Removed adapter registration from src/ExtractorFactory.php
• Deleted src/Adapters/Sassmeister/ directory (Extractor and Code detector)
• Removed testSassmeister() test method from tests/PagesTest.php
• Deleted test fixtures and cached responses

ref

• Make snapshot updates possible without modifying test code #564