[BUG] [java] deprecated call to RequestBody.create

Created by: ashatch

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

okhttp-gson/ApiClient.mustache has a deprecated call to RequestBody.create() (parameter reorder).

openapi-generator version

master

Suggest a fix

I'll raise a PR...