[Upgrade Assistant] Remove unnecessary mappings for ml snapshots (#15…

…1014)

## Summary
Partially addresses #64547
Follow up to #150878

This PR removes unnecessary mappings from the saved objects type
`upgrade-assistant-ml-upgrade-operation. This saved objects are used to
store the resolution progress of ml snapshot deprecations.

Currently, the ml deprecations are disabled via a config for Upgrade
Assistant plugin `xpack.upgrade_assistant.featureSet.mlSnapshots`. And
ES will probably not let us use any old ml snapshots in the 8.x version.

### How to test
1. Add `xpack.upgrade_assistant.featureSet.mlSnapshots: true` to your
`kibana.dev.yml` file
2. Start ES and Kibana with `yarn es snapshot --license=trial` and `yarn
start`
3. Add a sample data set, for example `kibana_sample_data_flights`.
4. Navigate to Analytics -> Machine Learning -> Anomaly Detection ->
Jobs.
5. Create a job for a single metric, chose a time range with some data
in it. Memorize the value you input for job ID.
6. Start and stop the job's datafeed a couple of times, so that you have
more than 1 snapshot. Memorize the value of the snapshot ID.
7. replace `deprecations` on line 22 in the file
[`/server/lib/es_deprecations_status.ts`](https://github.com/elastic/kibana/blob/main/x-pack/plugins/upgrade_assistant/server/lib/es_deprecations_status.ts#L22)
with
```
  const deprecations = {
    cluster_settings: [],
    node_settings: [],
    ml_settings: [
      {
        level: 'critical',
        message:
          'model snapshot [1676291073] for job [test_123] needs to be deleted or upgraded',
        url: '',
        details: 'details',
        _meta: { snapshot_id: '1676291073', job_id: 'test_123' },
        resolve_during_rolling_upgrade: false,
      },
    ],
    index_settings: {},
  };
```
where `job_id` and `snapshot_id` are values from step 5 and 6.
8. open UA and test the resolution of the ml snapshot deprecation.

src/core/server/integration_tests/saved_objects/migrations/group2/check_registered_types.test.ts

@@ -143,7 +143,7 @@ describe('checking migration metadata changes on all registered SO types', () =>
         "task": "ebcc113df12f14bf627dbd335ba78507187b48a3",
         "telemetry": "561b329aaed3c15b91aaf2075645be3097247612",
         "ui-metric": "410a8ad28e0f44b161c960ff0ce950c712b17c52",
-        "upgrade-assistant-ml-upgrade-operation": "e20ff1efa3c4757f5e7ff5fb897c557b08524c3a",
+        "upgrade-assistant-ml-upgrade-operation": "d8816e5ce32649e7a3a43e2c406c632319ff84bb",
         "upgrade-assistant-reindex-operation": "09ac8ed9c9acf7e8ece8eafe47d7019ea1472144",
         "upgrade-assistant-telemetry": "12bcbfc4e4ce64d2ca7c24f9acccd331a2bd2ab6",
         "uptime-dynamic-settings": "9a63ce80904a04be114749e426882dc3ff011137",

x-pack/plugins/upgrade_assistant/server/saved_object_types/ml_upgrade_operation_saved_object_type.ts

@@ -14,16 +14,8 @@ export const mlSavedObjectType: SavedObjectsType = {
   hidden: false,
   namespaceType: 'agnostic',
   mappings: {
+    dynamic: false,
     properties: {
-      nodeId: {
-        type: 'text',
-        fields: {
-          keyword: {
-            type: 'keyword',
-            ignore_above: 256,
-          },
-        },
-      },
       snapshotId: {
         type: 'text',
         fields: {
@@ -33,24 +25,6 @@ export const mlSavedObjectType: SavedObjectsType = {
           },
         },
       },
-      jobId: {
-        type: 'text',
-        fields: {
-          keyword: {
-            type: 'keyword',
-            ignore_above: 256,
-          },
-        },
-      },
-      status: {
-        type: 'text',
-        fields: {
-          keyword: {
-            type: 'keyword',
-            ignore_above: 256,
-          },
-        },
-      },
     },
   },
 };