Documentation update for issue #29

[quantstruct-canvas-preview]

Attempt to resolve issue 29

To align with the documentation style guide, I identified two instances where a leading article precedes a product name or where capitalization consistency could be improved:

• content/nms/nginx-agent/_index.md has a front matter description starting with "Learn about the NGINX Agent" but the word "the" is a definite article preceding the product name, which should be removed.
• content/nginx-one/metrics/enable-metrics.md starts with "The NGINX One Console dashboard..." where the leading article should be removed to say "NGINX One Console dashboard...". This also reinforces consistent capitalization of NGINX-related terms.

I prepared a minimal change plan for these two documents to implement the requested style updates without changing other content.