fix: correct string quotation in city scope

- Change single quotes to double quotes for adapter name check

This change ensures consistent usage of double quotes in the
conditional check for the SQLite adapter. It does not affect
any functionality but improves code readability.

app/models/city.rb

@@ -38,7 +38,7 @@ class City < ApplicationRecord
   }
 
   scope :least_popular_active, -> {
-    if ActiveRecord::Base.connection.adapter_name.downcase == 'sqlite'
+    if ActiveRecord::Base.connection.adapter_name.downcase == "sqlite"
       active
         .joins("LEFT JOIN ahoy_events ON json_extract(ahoy_events.properties, '$.city_id') = cities.id
                AND json_extract(ahoy_events.properties, '$.event_type') = 'city_view'")