chore: Move to reading the new env vars

[honnix]

TL;DR

Stop reading the removed envs (done in https://github.com/flyteorg/flyte/pull/6614).

Type

• [x] Bug Fix
• [ ] Feature
• [ ] Plugin

Are all requirements met?

• [x] Code completed
• [ ] Smoke tested
• [ ] Unit tests added
• [ ] Code documentation added
• [ ] Any pending items have an associated Issue

Complete description

These envs had been deprecated forever and eventually got removed from Flyte backend. So here we switch to reading the new envs.

Tracking Issue

NA

Follow-up issue

NA