[ML] [META] Audit routes with no validation

[jgowdyelastic]

For serverless all routes should have strict validation.
We have 19 routes which do not have validation and so I wanted to check each one to ensure this was correct.

Each of the 19 routes listed below use the GET method and do not take any parameters, therefore no validation is necessary.

x-pack/plugins/ml/server/routes/anomaly_detectors.ts:
GET /internal/ml/anomaly_detectors
GET /internal/ml/anomaly_detectors/_stats

x-pack/plugins/ml/server/routes/calendars.ts:
GET /internal/ml/calendars

x-pack/plugins/ml/server/routes/data_frame_analytics.ts:
GET /internal/ml/data_frame/analytics/_stats

x-pack/plugins/ml/server/routes/datafeeds.ts:
GET /internal/ml/datafeeds
GET /internal/ml/datafeeds/_stats

x-pack/plugins/ml/server/routes/filters.ts:
GET /internal/ml/filters
GET /internal/ml/filters/_stats

x-pack/plugins/ml/server/routes/job_service.ts:
GET /internal/ml/jobs/jobs_with_geo
GET /internal/ml/jobs/groups
GET /internal/ml/jobs/blocking_jobs_tasks,
GET /internal/ml/jobs/all_jobs_and_group_ids

x-pack/plugins/ml/server/routes/saved_objects.ts:
GET /internal/ml/saved_objects/status
GET /internal/ml/saved_objects/jobs_spaces
GET /internal/ml/saved_objects/trained_models_spaces

x-pack/plugins/ml/server/routes/system.ts:
GET /internal/ml/ml_capabilities
GET /internal/ml/ml_node_count
GET /internal/ml/info

x-pack/plugins/ml/server/routes/trained_models.ts:
GET /internal/ml/trained_models/_stats

[elasticmachine]

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