Update Tempo documentation, Agent-->Alloy

[clayton-cornell]

This issue tracks the work for updating Agent-->Alloy in the Tempo documentation.

### Tasks
- [ ] Identify the topics that reference or document using Agent with Alloy
- [ ] Assess the contents for minor update, rewrite, or remove.

[clayton-cornell]

Initial scan of Tempo docs shows multiple hits on Agent in these topics:

• tempo/configuration/grafana-agent/automatic-logging.md
• tempo/configuration/grafana-agent/tail-based-sampling.md
• tempo/configuration/grafana-agent/_index.md
• tempo/configuration/grafana-agent/service-graphs.md
• tempo/metrics-generator/service-graph-view.md
• tempo/metrics-generator/_index.md
• tempo/metrics-generator/span_metrics.md
• tempo/metrics-generator/service_graphs/enable-service-graphs.md
• tempo/operations/monitor/set-up-monitoring.md
• tempo/operations/architecture.md
• tempo/setup/set-up-test-app.md
• tempo/getting-started/example-demo-app.md
• tempo/getting-started/_index.md
• tempo/troubleshooting/agent.md
• tempo/troubleshooting/unable-to-see-trace.md
• tempo/troubleshooting/_index.md

[github-actions[bot]]

This issue has not had any activity in the past 30 days, so the needs-attention label has been added to it. If the opened issue is a bug, check to see if a newer release fixed your issue. If it is no longer relevant, please feel free to close this issue. The needs-attention label signals to maintainers that something has fallen through the cracks. No action is needed by you; your issue will be kept open and you do not have to respond to this comment. The label will be removed the next time this job runs if there is new activity. Thank you for your contributions!