[8.6] [DOCS] Add specifications for deprecated alert APIs (#149655)

[kibanamachine]

Backport

This will backport the following commits from main to 8.6:

• [DOCS] Add specifications for deprecated alert APIs (#149655)

Questions ?

Please refer to the Backport tool documentation

[github-actions]

Documentation preview:

• ✨ Changed pages

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: eb3e650

Metrics [docs]

Unknown metric groups

ESLint disabled in files

id	before	after	diff
osquery	1	2	+1

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	19	21	+2
fleet	61	67	+6
osquery	108	113	+5
securitySolution	441	447	+6
total			+19

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	20	22	+2
fleet	69	75	+6
osquery	109	115	+6
securitySolution	518	524	+6
total			+20

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @lcawl