Check SourceSpy

[koppor]

As reported by our link checker, SourceSpy is down:

We are ignoring the site at link checks from now on: 865bf3c to get PRs working: #6675 (comment)

I did not find any public announcement, but will contact @SourceSpyTeam (I found their GitHub profile) to ask about their future.

[tobiasdiez]

As the build fails again because some link is (temporarily) down, I think the link checker should work similar to the fetcher tests (i.e. don't run every time etc) and not as part of the checkstyle tests...

[koppor]

I wrote the SourceSpy guys. No reply yet. We still need to keep the check to be reminded that the site is down. Nevertheless files a PR moving the check to a monthly one. See #6695.

[Siedlerchr]

It's working again, so I close this issue.