remove collector registry

[charlienegri]

Summary: I think that the extra CollectorRegistry() broke the metrics, the standard flask collector does not work anymore at the moment https://dmci.s-enda-dev.k8s.met.no/metrics, so trying to remove it. testing with a local container still exposes everything so hard to tell if this will fix..

Related issue: #220

Suggested reviewer(s):

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• 100% test coverage of new code - meaning:
  • The overall test coverage increased or remained the same as before
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• All tests are passing
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The checklist is based on the S-ENDA conventions and definition of done (see General Conventions). The above points are not necessarily relevant to all contributions. In that case, please add a short explanation to help the reviewer.

[magnarem]

approved