docs: Refactor finish_reason property in ChatCompletionChoice (#24)

Replaced finish_reason property with a reference to FinishReason schema.

Author: edenreich

openapi.yaml

@@ -1064,25 +1064,7 @@ components:
       type: object
       properties:
         finish_reason:
-          type: string
-          description: >
-            The reason the model stopped generating tokens. This will be
-            `stop` if the model hit a natural stop point or a provided
-            stop sequence,
-
-            `length` if the maximum number of tokens specified in the
-            request was reached,
-
-            `content_filter` if content was omitted due to a flag from our
-            content filters,
-
-            `tool_calls` if the model called a tool.
-          enum:
-            - stop
-            - length
-            - tool_calls
-            - content_filter
-            - function_call
+          $ref: '#/components/schemas/FinishReason'
         index:
           type: integer
           description: The index of the choice in the list of choices.