fix(operator): Update OTLP user guide to reflect change in LokiStack

[xperimental]

What this PR does / why we need it:

Follow-up of #15857 updating the documentation to match.

Which issue(s) this PR fixes:

Refs LOG-6507

Special notes for your reviewer:

• I think this PR represents the minimal change we need, so that the documentation matches the operator's reality again. While reading through the article again, I noticed that it might need further improvement, which this PR does not include (yet). We can either wait until this change is included in this PR or split the rework of the article out into a separate PR, I'm fine either way.

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Title matches the required conventional commits format, see here