[ROCm][CI] Route gfx942 unittests to rocOps ecosystem runners

Switch the unittests-rocm job runner label from
amd-vtr-linux.rocm.gpu.gfx942.1 to linux.rocm.gpu.ecosystem.gfx950.1,
the rocOps-managed ecosystem runner scale set for downstream PyTorch
ecosystem repos.

Made with Cursor

Author: amdfaa

.github/workflows/tests.yml

@@ -54,7 +54,7 @@ jobs:
       matrix:
         python-version:
           - "3.10"
-        runner: ["amd-vtr-linux.rocm.gpu.gfx942.1"]
+        runner: ["linux.rocm.gpu.ecosystem.gfx950.1"]
         gpu-arch-type: ["rocm"]
         gpu-arch-version: ["7.1"]
       fail-fast: false