Remove gopher case from origin algorithm

After #453 the gopher scheme is not special anymore. According to web-platform-tests/wpt#19770 the intention is that a gopher URL's origin would be opaque (null). Fixes part of #455.

Author: rmisev

url.bs

@@ -2444,7 +2444,6 @@ background information. [[!HTML]]
   (<code>https</code>, <code>whatwg.org</code>, null, null).
 
  <dt>"<code>ftp</code>"
- <dt>"<code>gopher</code>"
  <dt>"<code>http</code>"
  <dt>"<code>https</code>"
  <dt>"<code>ws</code>"