Collector config: don't link to deprecated ServiceTelemetryMetrics struct

[chalin]

Originally posted by @chalin in #3443 (comment)

As I mentioned in the other PR making changes to this section, I don't think we should be linking out to the source file. Especially because that config file has been deprecated!

We should just list the "full options" (there aren't that many) here.

---

If you choose to keep the link for now, I'd at least suggest the following rewording to avoid a "here" link:

for scraping at <http://localhost:8888/metrics>. For the full list of options
for the `metrics` subsection, see the 
[`ServiceTelemetryMetrics struct`](https://github.com/open-telemetry/opentelemetry-collector/blob/7666eb04c30e5cfd750db9969fe507562598f0ae/config/service.go#L99-L111) comments.

References

This is the link info the config file:

• https://github.com/open-telemetry/opentelemetry-collector/blob/7666eb04c30e5cfd750db9969fe507562598f0ae/config/service.go#L99-L111

/cc @open-telemetry/collector-approvers @theletterf

[tiffany76]

I think we can close this issue. The link in question was removed in #4504.

[svrnm]

@chalin PTAL for closing this

[chalin]

Thanks, I'll take @tiffany76's word for it.