ci(gfx11): temporarily disable gfx1151 hardware test (runner offline)

[jimw567]

Summary

The linux-gfx1151-gpu-rocm self-hosted runner is currently offline, so the test-gfx job sits queued indefinitely and blocks create-release — the nightly can build but never publishes. This temporarily disables the hardware test so releases flow again.

Changes

• test-gfx: gated off via if: false && ... (job body kept intact so re-enabling is a one-line revert).
• create-release: dropped test-gfx from needs and removed the needs.test-gfx.result == 'success' gate. Still requires build-ubuntu success + workflow_dispatch + create_release=true, so push/PR still never release.

Revert plan

When the gfx1151 runner is back online, restore:

1. test-gfx if: needs.build-ubuntu.result == 'success'
2. create-release needs: [build-ubuntu, test-gfx] + the needs.test-gfx.result == 'success' line

Both spots carry TODO comments pointing at each other.

Context

Three nightly dispatches (build-ubuntu green) are stuck queued on the missing runner right now; this unblocks them / future nightlies from publishing. Correctness of the multiarch package is still validated at build time; only the on-device inference smoke test is paused.

Test plan

• Dispatch with create_release=true and confirm: build succeeds, test-gfx is skipped, create-release runs and publishes.
• Confirm push/PR still builds only and never releases.