fix for MapperException[the [enabled] parameter can't be updated for the object mapping [metadata.source_to_query_index_mapping]

[sbcd90]

Issue #, if available:

Description of changes:

when the source_to_query_index_mapping field is upserted without the .opendistro-alerting-config index present, the mapping for it gets corrupted.

"source_to_query_index_mapping": {
  "properties": {
    "ocsf_api_activityXnRAfI0B9Qgmh2Pzq4q4": {
      "type": "text",
      "fields": {
        "keyword": {
          "type": "keyword",
          "ignore_above": 256
        }
      }
    }
  }
}

the correct mapping for the field is,

"source_to_query_index_mapping": {
  "type": "object",
  "enabled": false
}

this pr ensures that the upsert doesn't happen if the index is not present.

the test case will be removed before merging the pr once pr review is complete.

CheckList:

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