refactor: simplify scope limit parameters

- Change `limit:` to `limit =` in the scopes for
  `latest` and `by_popularity`.
- This allows for a default value of 100 to be used
  if no argument is provided, making the code more
  user-friendly and consistent.

This refactor does not alter the behavior of the
existing functionality but streamlines the syntax.

app/models/weather_art.rb

@@ -12,11 +12,11 @@ class WeatherArt < ApplicationRecord
   validates :weather_date, presence: true
   validates :city_id, presence: true
 
-  scope :latest, ->(limit: 100) {
+  scope :latest, ->(limit = 100) {
     order(created_at: :desc).limit(limit)
   }
 
-  scope :by_popularity, ->(limit: 100) {
+  scope :by_popularity, ->(limit = 100) {
     if ActiveRecord::Base.connection.adapter_name.downcase == "sqlite"
       joins("LEFT JOIN ahoy_events ON json_extract(ahoy_events.properties, '$.weather_art_id') = weather_arts.id
              AND json_extract(ahoy_events.properties, '$.event_type') = 'weather_art_view'")