[8.x] Fix index templates api integration tests

[ElenaStoeva]

Fixes #209027

Summary

This PR updates the 8.x index templates API integration tests to fix the failures in the 8.x -> 9.0 forward compatibility tests.

To run the forward-compatibility tests locally:

ES_SNAPSHOT_MANIFEST="https://storage.googleapis.com/kibana-ci-es-snapshots-daily/9.0.0/manifest-latest-verified.json" node scripts/functional_tests_server.js --config ./x-pack/test/api_integration/apis/management/config.ts

and

ES_SNAPSHOT_MANIFEST="https://storage.googleapis.com/kibana-ci-es-snapshots-daily/9.0.0/manifest-latest-verified.json" node scripts/functional_test_runner.js --config ./x-pack/test/api_integration/apis/management/config.ts --grep="index templates"

[elasticmachine]

Pinging @elastic/kibana-management (Team:Kibana Management)

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 51b8525

Failed CI Steps

• Jest Tests #5

Test Failures

• [job] [logs] Jest Tests #5 / notesSlice notesReducer fetchNotesByDocumentIds should replace notes when success on fetch notes by document ids on a non-empty state
• [job] [logs] Jest Tests #5 / notesSlice notesReducer fetchNotesBySavedObjectIds should replace notes when success on fetch notes by saved object id ids on a non-empty state

Metrics [docs]

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
@kbn/test-suites-xpack	753	754	+1

Total ESLint disabled count

id	before	after	diff
@kbn/test-suites-xpack	779	780	+1

cc @ElenaStoeva

[SoniaSanzV]

lgtm, thank you @ElenaStoeva :)