[BUG] Kotlin ApiClient leaks okhttp3.Response.

[gosusnp]

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

We tracked down a memory leak from the generated api client in kotlin.
The okhttp3.Response is closeable and isn't closed. This commit shows the fix we did on our end that addressed the leak.

openapi-generator version

We were using 0.6.2, we migrated to 7.6.0however, looking at the generated code, I believe the issue remains.

OpenAPI declaration file content or url

Generation Details

Steps to reproduce

Generate a kotlin client, keep on calling any requests, see memory usage keeps going up.

Related issues/PRs

Suggest a fix

Suggested fix: #18997