clarify which request to explore in APM

[swaretech]

Requirements

• [ x] Content follows Splunk guidelines for style and formatting.
• [ x] You are contributing original content.

Describe the change

Enter a description of the changes, why they're good for the Observability Cloud documentation, and so on.
Adding a couple of descriptors so it's clearer why Kai is clicking this particular APM link in the Synthetics waterfall.

If this contribution is time sensitive, tell us when you'd like this PR to be merged.
n/a

[theletterf]

Thanks!