Remove `report_metrics` from indexer manifest

[ra0x3]

• This flag was added at a time when we thought we'd report indexer metrics of some kind
• This can be removed, as we're not going that route

[dadepo]

I'll look into picking this next. @ra0x3 any potential spooky action at a distance removing this might cause? :)

[ra0x3]

@dadepo

• A simple grep for report_metrics should do the trick. Will want to remove references from the code and the docs
  • But be warned the code might not actually be there, it might merely be a probability wave, and removing it might only cause it to "re-appear" somewhere else ;)