update metrics-api scaler doc related to fetching metrics from kubernetes service

[julianguinard]

this related to the addition of aggregateFromKubeServiceEndpoints and aggregationType parameters in PR 6565, used to fetch/aggregate metrics from a kubernetes service's list of endpoints

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[zroubalik]

Could you please add a paragraph below Parameter list explaining this new feature? Basically a gist of the code PR description would be great

[julianguinard]

Could you please add a paragraph below Parameter list explaining this new feature? Basically a gist of the code PR description would be great

Hello @zroubalik , I just added a shorter version of the code PR description in a new paragraph for the metrics the docs here

[JorTurFer]

Could you move this to the file for v2.18 instead of v2.17?

[julianguinard]

Could you move this to the file for v2.18 instead of v2.17?

Sure, I closed this PR by accident & opened a new one here so doc is moved to 2.18