API: remove various associated fields included by default.

Remove various associated fields that were included by default on
certain endpoints. API users can use the only param to include the
full association if they need these fields.

* /artists.json: urls.
* /artist_urls.json: artist.
* /comments.json: creator_name and updater_name.
* /notes.json: creator_name.
* /pools.json: creator_name.
* /posts.json: uploader_name, children_ids, pixiv_ugoira_frame_data.
* /post_appeals.json: is_resolved.
* /post_versions.json: updater_name.
* /uploads.json: uploader_name.

app/models/artist.rb

@@ -4,7 +4,6 @@ class Artist < ApplicationRecord
 
   attr_accessor :url_string_changed
   array_attribute :other_names
-  api_attributes including: [:urls]
 
   before_validation :normalize_name
   before_validation :normalize_other_names