Updating search engines list does not update the default search engine

[jonalmeida]

Steps to reproduce

1. Run Focus iOS at least once; make one search.
2. Change the Search/SearchEngines.plist for your locale to have a different default and rebuild the app.
3. Run Focus iOS again; make another search.

Expected behaviour

• The search engine used should be based on the new default if no user changes have occurred.

Actual behaviour

• The search engine used is based on a cached version that only happens on first run or when a user changes it.

Device & build information

• Device: n/a
• Build version: main @ cf48674

cc: @nbhasin2

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