Remove IBM GenAI support following sunset

[yoavkatz]

genai service was sunset, we should remove all references to it from Unitxt code base

[github-actions]

This issue is stale because it has been open for 30 days with no activity.

[github-actions]

This issue was closed because it has been inactive for 14 days since being marked as stale.

[github-actions]

This issue is stale because it has been open for 30 days with no activity.

[yoavkatz]

KEep open.

[github-actions]

This issue is stale because it has been open for 30 days with no activity.

[yoavkatz]

Working on it in #1508

[github-actions]

This issue is stale because it has been open for 30 days with no activity.