config: remove enable_image_cropping option.

There's no need to disable this option. Supporting it adds complexity
and disabling it is untested.

app/logical/danbooru_image_resizer.rb

@@ -27,8 +27,6 @@ module DanbooruImageResizer
   end
 
   def crop(file, width, height, resize_quality = 90)
-    return nil unless Danbooru.config.enable_image_cropping
-
     output_file = Tempfile.new
     resized_image = Vips::Image.thumbnail(file.path, width, height: height, **CROP_OPTIONS)
     resized_image.jpegsave(output_file.path, Q: resize_quality, **JPEG_OPTIONS)

app/logical/pixiv_ugoira_converter.rb

@@ -69,8 +69,6 @@ class PixivUgoiraConverter
   end
 
   def self.generate_crop(ugoira_file)
-    return nil unless Danbooru.config.enable_image_cropping
-
     file = Tempfile.new(["ugoira-crop", ".zip"], binmode: true)
     zipfile = Zip::File.new(ugoira_file.path)
     zipfile.entries.first.extract(file.path) { true } #  'true' means overwrite the existing tempfile.

app/presenters/post_presenter.rb

@@ -43,7 +43,7 @@ class PostPresenter
 
     locals[:tooltip] = "#{post.tag_string} rating:#{post.rating} score:#{post.score}"
 
-    locals[:cropped_url] = if Danbooru.config.enable_image_cropping && options[:show_cropped] && post.has_cropped? && !CurrentUser.user.disable_cropped_thumbnails?
+    locals[:cropped_url] = if options[:show_cropped] && post.has_cropped? && !CurrentUser.user.disable_cropped_thumbnails?
       post.crop_file_url
     else
       post.preview_file_url

app/views/posts/partials/index/_posts.html.erb

@@ -1,4 +1,4 @@
-<div id="posts" class="user-disable-cropped-<%= Danbooru.config.enable_image_cropping && CurrentUser.user.disable_cropped_thumbnails? %>">
+<div id="posts" class="user-disable-cropped-<%= CurrentUser.user.disable_cropped_thumbnails? %>">
   <div id="posts-container">
     <%= post_set.post_previews_html(self) %>
   </div>

app/views/recommended_posts/_index.html.erb

@@ -1,4 +1,4 @@
-<section class="recommended-posts user-disable-cropped-<%= Danbooru.config.enable_image_cropping && CurrentUser.user.disable_cropped_thumbnails? %>">
+<section class="recommended-posts user-disable-cropped-<%= CurrentUser.user.disable_cropped_thumbnails? %>">
   <% if @recs.empty? %>
     No recommendations found.
   <% end %>

config/danbooru_default_config.rb

@@ -502,10 +502,6 @@ module Danbooru
     def recaptcha_secret_key
     end
 
-    def enable_image_cropping
-      true
-    end
-
     # Akismet API key. Used for Dmail spam detection. http://akismet.com/signup/
     def rakismet_key
     end