fix: update observability documentation

[caalador]

Update the documentation of
observability-kit to match
changes that made statements faulty.

[github-actions]

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URL: https://docs-preview-pr-5958.fly.dev

Changed pages

Added content is highlighted in green; removed content is marked in red on each page.

• tools/observability/configuration — modified, +7/-6 lines, 5 removal marker(s)
• tools/observability/insights — modified, +30/-10 lines, 9 removal marker(s)
• tools/observability/reference — modified, +4/-2 lines, 2 removal marker(s)

Built from 9d9a981

[heruan]

The edits themselves are accurate: three collectors, tripled capacity, getRecentClientErrors(), the grouping keys, the client counter descriptions and the client property all match the kit.

Since this PR was opened, two kit changes made more of reference.adoc stale. They are outside the diff, so listing them here rather than inline:

• Lines 498, 522 and 572 still name the span vaadin.ui.access. It was renamed to vaadin.executor.task in vaadin/observability-kit#397. The scope is now "tasks submitted to the Vaadin service executor" (signal effects, signal result notifications, application tasks), not every UI.access.
• Line 540 lists the request types as uidl, heartbeat, push, static, other. vaadin/observability-kit#399 added bootstrap and stream.

Optional: the replay example in insights.adoc around line 168 shows the production format only. Since vaadin/observability-kit#400, development mode adds view state steps such as Set the 'Reason' Select to 'Defective' and Click the 'Process return' Button. A sentence on that difference would help, but it can also be a follow-up.