DEV: Remove logical OR assignment of constants (#29201)

Constants should always be only assigned once. The logical OR assignment
of a constant is a relic of the past before we used zeitwerk for
autoloading and had bugs where a file could be loaded twice resulting in
constant redefinition warnings.

lib/onebox/engine/youtube_onebox.rb

@@ -10,8 +10,8 @@ module Onebox
       requires_iframe_origins "https://www.youtube.com"
       always_https
 
-      WIDTH ||= 480
-      HEIGHT ||= 360
+      WIDTH = 480
+      HEIGHT = 360
 
       def parse_embed_response
         return unless video_id

lib/onebox/helpers.rb

@@ -7,7 +7,7 @@ module Onebox
     class DownloadTooLarge < StandardError
     end
 
-    IGNORE_CANONICAL_DOMAINS ||= %w[www.instagram.com medium.com youtube.com]
+    IGNORE_CANONICAL_DOMAINS = %w[www.instagram.com medium.com youtube.com]
 
     def self.clean(html)
       html.gsub(/<[^>]+>/, " ").gsub(/\n/, "")

lib/onebox/preview.rb

@@ -5,7 +5,7 @@ module Onebox
     # see https://bugs.ruby-lang.org/issues/14688
     client_exception =
       defined?(Net::HTTPClientException) ? Net::HTTPClientException : Net::HTTPServerException
-    WEB_EXCEPTIONS ||= [
+    WEB_EXCEPTIONS = [
       client_exception,
       OpenURI::HTTPError,
       Timeout::Error,

lib/onebox/sanitize_config.rb

@@ -107,7 +107,7 @@ module Onebox
         ),
       )
 
-    DISCOURSE_ONEBOX ||=
+    DISCOURSE_ONEBOX =
       Sanitize::Config.freeze_config(
         Sanitize::Config.merge(
           ONEBOX,