[BUG][C#][API client: csharp] Integer Enumeration produce same code as String Enumeration

Description

When generatin API client for C#. the code for Integer Enumerator produce have the same properties as if it was a String Enumerator.

openapi-generator version

4.2.0

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  version: "1"
  title: BUG Report
paths:
  /Create:
    put:
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/new_item'
      responses:
        default:
          description:  return
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/new_item'
components:
  schemas:
    new_item:
      properties:
        class:
          type: string
          enum:
            - high
            - low
        size:
          type: integer
          format: int8
          enum:
            - 2
            - 4
            - 8

Command line used for generation

java -jar openapi-generator-cli.jar generate -i my.yaml -g csharp

Steps to reproduce

Just run the command and compare JSON attribute of "enum ClassEnum" and "enum SizeEnum" at src/Org.OpenAPITools/Model/NewItem.cs

Related issues/PRs

Resamble but more simple then:
https://github.com/OpenAPITools/openapi-generator/issues/3246

Suggest a fix

The JSON attribute "[JsonConverter(typeof(StringEnumConverter))]" should be used on string Enomurators,
but should be omit in case of Integer Enomurators.

Start by generating the C# client with the provided OpenAPI YAML and command, then compare the enum declarations in src/Org.OpenAPITools/Model/NewItem.cs. Check the JSON attributes on ClassEnum and SizeEnum; done means string enums retain StringEnumConverter while integer enums do not.