[BUG] [R] Invalid syntax for lists default parameters - uses brackets instead of `list()`

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

The R generator creates default list values [] which is not valid R code (should be list()).

openapi-generator version

openapi-generator-cli 7.8.0-SNAPSHOT

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: Sample API
  version: 0.0.0
paths:
  /:
    get:
      responses:
        '200': 
          description: Foo
          content:
            application/json:
              schema: 
                $ref: "#/components/schemas/ExampleSchema"
components:
  schemas:
    ExampleSchema:
      properties:
        field:
          items:
            type: string
          type: array
          default: []
      type: object
      title: ExampleSchema

Steps to reproduce

openapi-generator-cli generate \                                     
          -i openapi.json \
          -g r \
          -o ./output

Relevant R code:

./output/R/example_schema.R

    initialize = function(`field` = [], ...) {

This should have been:

    initialize = function(`field` = list(), ...) {

This also applies to the default arguments to requests - I can file a separate ticket but I'd assume it's the same underlying code

Reproduce the issue with the supplied OpenAPI declaration and the openapi-generator-cli generate command, then inspect ./output/R/example_schema.R. Trace how the R generator turns array defaults into request and model arguments. Done means generated R defaults use list() rather than [], including request arguments, and the generated code is valid R.