If you use a External Wiki, with Gitea, it brings currently 2 Problems
in the Header:
1. It always uses the Wiki Icon. When you use e.g. a External Issue
Tracker, it shows the External Link icon to Indicate, that the User will
send to a External Side. This helps preventing fishing.
2. If you use a External Wiki, the Link in the Header still goes to
`{repo}/wiki` which will redirect the user to the External Wiki. That
means, that if the users hovers with the Cursor over the link, it shows
`{repo}/wiki`, so the User does not know, where he will land.
This PR fixes both.
d347208114
