[Internal]: Update APM Service Map docs after Focus Map deprecation

### Description

What: Update APM Service Map docs to remove the legacy Focus Map / per-service Service Map tab model and describe the current UX.

When: As soon as possible, the UI change has landed ([elastic/kibana#272175](https://github.com/elastic/kibana/issues/272175), closed 2026-07-29).

Why: Public docs still describe Global vs Service-specific maps and the Focus map CTA. After the UI change:

- There is no dedicated Service map tab on service views (web + mobile)
- Users see embedded / contextual maps on Overview, transaction detail, and elsewhere
- Explore in Service map opens the global Service Map, with context preserved via service.name filters / highlighting (including multi-service highlight from the query)

Primary page: https://www.elastic.co/docs/solutions/observability/apm/service-map

Please also review:

- https://www.elastic.co/docs/solutions/observability/apm/services (likely no change; quick check)
- Any screenshots/GIFs that show the removed tab or Focus map CTA

### Resources

- Tracking / scope: https://github.com/elastic/observability-dev/issues/5897
- Parent deprecation: https://github.com/elastic/observability-dev/issues/5578
- UI implementation: https://github.com/elastic/kibana/issues/272175
- Related embed work: https://github.com/elastic/kibana/issues/272173, https://github.com/elastic/kibana/issues/272174

### Which deployment methods does this change impact?

Elastic On-Prem and Cloud (all)

### Feature differences

Identical across all

### What Elastic Stack release is this request related to?

9.6

### Serverless release

Already released

### Collaboration model

Unknown

### Point of contact.

**Main contact:** @MiriamAparicio

**Stakeholders:** @cpipilas

Start with the APM Service Map page and review the Services page, using Kibana issues 272175, 272173, and 272174 to confirm the current UX. Remove descriptions and screenshots of the deprecated Focus Map and dedicated service-map tab, and document embedded maps plus Explore in Service map with preserved service.name context; done when the affected docs match the released UI.

Written by the indexing model from the issue text.