[8.6](backport #3476) [apm docs consolidation] Clean up

[mergify]

This is an automatic backport of pull request #3476 done by Mergify.
Cherry-pick of d4309b5 has failed:

On branch mergify/bp/8.6/pr-3476
Your branch is up to date with 'origin/8.6'.

You are currently cherry-picking commit d4309b55.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   docs/en/apm-server/api-error.asciidoc
	modified:   docs/en/apm-server/api-event-example.asciidoc
	modified:   docs/en/apm-server/api-metadata.asciidoc
	modified:   docs/en/apm-server/api-metricset.asciidoc
	modified:   docs/en/apm-server/api-span.asciidoc
	modified:   docs/en/apm-server/api-transaction.asciidoc
	deleted:    docs/en/apm-server/data/elasticsearch/generated/errors.json
	deleted:    docs/en/apm-server/data/elasticsearch/generated/rum_v3_errors.json
	deleted:    docs/en/apm-server/data/elasticsearch/generated/rum_v3_transactions.json
	deleted:    docs/en/apm-server/data/elasticsearch/generated/spans.json
	deleted:    docs/en/apm-server/data/elasticsearch/generated/transactions.json
	deleted:    docs/en/apm-server/data/intake-api/generated/events.ndjson
	deleted:    docs/en/apm-server/data/intake-api/generated/rum_v3_events.ndjson
	deleted:    docs/en/apm-server/data/intake-api/generated/sourcemap/bundle.js.map
	modified:   docs/en/apm-server/legacy/metadata-api.asciidoc
	modified:   docs/en/apm-server/legacy/metricset-api.asciidoc
	deleted:    docs/en/apm-server/spec/rumv3/error.json
	deleted:    docs/en/apm-server/spec/rumv3/metadata.json
	deleted:    docs/en/apm-server/spec/v2/error.json
	deleted:    docs/en/apm-server/spec/v2/metricset.json
	modified:   docs/en/apm-server/upgrading.asciidoc

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by them: docs/en/apm-server/apm-breaking.asciidoc
	both modified:   docs/en/apm-server/data-model.asciidoc
	deleted by them: docs/en/apm-server/data/elasticsearch/metricset.json
	both modified:   docs/en/apm-server/release-notes.asciidoc
	deleted by them: docs/en/apm-server/spec/rumv3/span.json
	deleted by them: docs/en/apm-server/spec/rumv3/transaction.json
	deleted by them: docs/en/apm-server/spec/v2/metadata.json
	deleted by them: docs/en/apm-server/spec/v2/span.json
	deleted by them: docs/en/apm-server/spec/v2/transaction.json

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[colleenmcginnis]

Blocked by elastic/apm-server#12261

[mergify]

This pull request has not been merged yet. Could you please review and merge it @colleenmcginnis? 🙏

[mergify]

This pull request has not been merged yet. Could you please review and merge it @colleenmcginnis? 🙏

[bmorelli25]

nice