Remove SERP Easter Egg Logo Toggle

[mikescamell]

Task/Issue URL: https://app.asana.com/1/137249556945/project/488551667048375/task/1212374007733022?focus=true

Description

Removes the SERP easter egg logo toggle. The feature has been out for a few months with no issues.

Steps to test this PR

Happy path

• Search for a term that has an Easter Egg logo (e.g., "predator", "terminator", "android" etc.)
• Verify the special logo appears in the omnibar
• Tap on the logo to see the enlarged version
• Tap anywhere on the screen to dismiss the enlarged view
• Enter a search term without special logo e.g. "monkeys"
• Verify the logo is replaced with the standard DuckDuckGo logo
• Search for a term that has an Easter Egg logo (e.g., "predator", "terminator", "android" etc.)
• Navigate away from the SERP page (by clicking a result) and verify the logo is replaced with the standard DuckDuckGo logo

UI changes

N/A

---

Note

Removes the SERP Easter Egg logo feature flag, simplifying SERP logo handling and updating UI/tests accordingly.

• Browser/State:
  • Remove SerpEasterEggLogosToggles usage and toggle gating from BrowserTabViewModel; evaluateSerpLogoState now always extracts SERP logo for DuckDuckGo query URLs and clears it otherwise.
• Omnibar UI:
  • Remove toggle checks in OmnibarLayout and OmnibarLayoutViewModel; always render standard DDG logo for Dax state and handle SerpLogo (including Easter Egg) directly in leading icon state.
• API:
  • Simplify SerpEasterEggLogosToggles by removing feature() method, leaving only self().
• Tests:
  • Update and simplify tests to reflect removal of the toggle, deleting disabled-path cases and adjusting expectations to always evaluate/extract or clear SERP logos based on URL.

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[landomen]

Looks good and works as expected 👍