Clarify remote swinfo network errors

[HebaruSan]

Background

#3817 added retrieval of remote swinfo.json files for KSP2 mods, which are very analogous to remote version files.

Problem

If the version_check property contains a URL that's a broken link, the error message isn't clear. It's just a generic 404 error that could be coming from anywhere:

Changes

Now that exception is caught and replaced with one indicating the context in which the error occurred:

$ netkan.exe --game KSP2 NetKAN/ManeuverNodeController.netkan
2233 [1] FATAL CKAN.NetKAN.Program (null) - Error fetching remote swinfo https://raw.githubusercontent.com/schlosrat/ManeuverNodeController/master/maneuver_node_controller/swinfo.json: The remote server returned an error: (404) Not Found.

I might self-review this since it only affects the bot and would be nice to have soon-ish.

[techman83]

Makes sense to me!