[DOCS]: API document for /v1/document/raw-text

[byzheng]

Description

API endpoint /v1/document/raw-text requires a title in the metadata. This requirement is missing in the document and example request. After execute the example, I get an error message

{
  "success": false,
  "error": "You are missing required metadata key:value pairs in your request. Required metadata key:values are 'title'"
}