Skip disabled repositories

[whiskeysierra]

We have a couple of disabled repositories and they yield errors in the log:

{
   "collector":"Repository",
   "file":"metrics_repository.go:127",
   "func":"collectRepository",
   "level":"error",
   "msg":"response status code is 404 (expected 200), url: https://dev.azure.com/gropyus/_apis/git/repositories/0ea2ea25-0d9d-4b4f-b3df-fbef5da3063d/commits?searchCriteria.fromDate=2021-10-07T06%3A03%3A51Z\u0026api-version=5.1",
   "project":"architecture",
   "repository":"base-image"
}

Even though it's not a big deal, it would be nice if disabled repositories were skipped by default.