NGF: Update telemetry doc for nginx one console connection metric

[salonichf5]

Proposed changes

• Updates telemetry documentation to add information about Nginx One Console connection metric.

Checklist

Before sharing this pull request, I completed the following checklist:

• I read the Contributing guidelines
• My branch adheres to the Git conventions
• My content changes adhere to the F5 NGINX Documentation style guide
• If my changes involve potentially sensitive information¹, I have assessed the possible impact
• I have waited to ensure my changes pass tests, and addressed any discovered issues

Footnotes

1. Potentially sensitive information includes personally identify information (PII), authentication credentials, and live URLs. Refer to the style guide for guidance about placeholder content. ↩

[sjberman]

This should target the ngf-release-2.1 branch because it's an unreleased feature (assuming that this functionality gets into 2.1)

[sjberman]

LGTM, just have to see if this gets into 2.1, otherwise we push to 2.2.