Clean up patch for SearchEngineSelector.sys.mjs.

Noticed in the 140-146 comparison. For 146 we removed the entire #getConfigurationOverrides method, yet the #getConfiguration method was left in its entirety. This is still the case in 147. I'm assuming that this was the linter complaining about an unused private method. Although #getConfiguration is also uncalled, maybe it escaped the linter since it calls itself!

I think we should clean up the patch to avoid commenting out whole methods and to make rebases easier to resolve.

@brizental or @pierov if you have an existing "Review" issue for this, can you please link it?