Use HTTPS when downloading unicode.org's emoji-test.txt (#37290)

lib/tasks/emojis.rake

@@ -60,7 +60,7 @@ end
 namespace :emojis do
   desc 'Generate a unicode to filename mapping'
   task :generate do
-    source = 'http://www.unicode.org/Public/emoji/16.0/emoji-test.txt'
+    source = 'https://www.unicode.org/Public/emoji/16.0/emoji-test.txt'
     codes  = []
     dest   = Rails.root.join('app', 'javascript', 'mastodon', 'features', 'emoji', 'emoji_map.json')