[DOCS] Incorrect use of updateable flag in Elasticsearch synonyms documentation

[ganiamine]

The documentation for Apply synonyms at index or search time contains an error in the example code for adding my_analyzer as a search analyzer.

The example includes the updateable flag in the field mapping for title, which results in the following error when used:

{
  "error": {
    "root_cause": [
      {
        "type": "mapper_parsing_exception",
        "reason": "unknown parameter [updateable] on mapper [title] of type [text]"
      }
    ],
    "type": "mapper_parsing_exception",
    "reason": "Failed to parse mapping: unknown parameter [updateable] on mapper [title] of type [text]",
    "caused_by": {
      "type": "mapper_parsing_exception",
      "reason": "unknown parameter [updateable] on mapper [title] of type [text]"
    }
  },
  "status": 400
}

To resolve the issue, the updateable flag should be applied to the token filter instead of the field mapping.

Suggested Fix:
Update the example to remove the updateable flag from the field mapping and ensure the token filter includes the correct configuration.