Test breaking docs semantically on CI

[findepi]

Summary by Sourcery

Test breaking documentation semantically in the CI pipeline by updating the user-mapping.json file

CI:

• Add semantic validation check for Sphinx docs in CI

Documentation:

• Modify user-mapping.json to introduce a semantic break in documentation

[findepi]

when docs are semantically broken it may be caught up by eg TestUserMapping.testDocsExample
test-docs (:trino-main) failed as expected ✅

[findepi]

when docs are semantically broken, and there also is some other code change, the regression may not be caught by CI ❌

[findepi]

filed

• CI may not catch a docs-testing test regression #27076