[BUG] generated code doesn't compile when @RequestMapping contains multiple values for produces attribute

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

In case of multiple media types that can be produced by the mapped handler, the values for the attribute produces in @RequestMapping annotation are not separated by a coma.

openapi-generator version

5.1.1

OpenAPI declaration file content or url

            responses:
                '200':
                    description: A file
                    content:
                        application/vnd.ms-excel:
                            schema:
                                type: string
                                format: binary
                '400':
                    $ref: '#/components/responses/BadRequest'

Generation Details

Gradle plugin task openApiGenerate
Generator spring

Compilation errors :

        error: '}' expected
        produces = { "application/vnd.ms-excel""application/json" },  

Extract of generated source code :

        produces = { "application/vnd.ms-excel""application/json" },  <--- missing comma here

Related issues/PRs

https://github.com/OpenAPITools/openapi-generator/issues/896

Reproduce the issue with the Gradle plugin task openApiGenerate using the spring generator and the supplied response media types. Inspect the generated @RequestMapping annotation where produces contains multiple values. The work is done when the generated Java source separates those values with commas and compiles successfully.