[rust][client] fix enum type usage

Created by: qavvvzdhwm

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PR description

The model template was referring to the enum name in the context instead of the enum-updated type.

openapi: 3.0.0
info:
  title: rust array of enums bug
  version: 1.0.0
paths:
  /:
    get:
      operationId: Op1
      tags:
        - array-enum
      responses:
        "200":
          description: ""
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ResponseFizzesBuzzes"
      requestBody:
        content:
          application/json:
            schema:
              type: integer
components:
  schemas:
    ResponseFizzesBuzzes:
      type: object
      properties:
        fizzes_buzzes:
          type: array
          items:
            type: string
            enum:
              - fizz
              - buzz
              - fizz_buzz
      required:
        - fizzes_buzzes

generated originally:

    pub fizzes_buzzes: FizzesBuzzes,

fixed:

    pub fizzes_buzzes: Vec<FizzesBuzzes>,

cc: @frol, @farcaller, @bjgill, @richardwhiuk