Issue title: [1840] Heiligenstadt errors on 2P/3P map
 Issue body: Heiligenstadt has an extra interchange on the 3P map not present on the printed map.
 Comments: 
 Comment 0: I suggest to add this to the implementation notes on the wiki if it won't be fixed.
{'source': 'GithubIssues', 'repo_name_with_owner': 'tobymao/18xx', 'issue_id': 1046234429, 'repo_stars': 205.0}