add neptune staff as code owners for neptune.py

[awaelchli]

What does this PR do?

As the title suggests, we welcome the neptune team to help us maintain the neptune logger integration.

Follow up to #6867

@kamil-kaczmarek

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Did you have fun?

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[kamil-kaczmarek]

hi @awaelchli ,

We happily take that role, as previously proposed in the #6867

@shnela @HubertJaworski @pkasprzyk @pitercl @Raalsky @aniezurawski @kamil-kaczmarek