[ROCm] set nvfuser default to disabled, keep CI (#86369)
Bug fix. nvfuser is functional for ROCm on gfx906, but some tests are failing for other gfx targets. Disable nvfuser until all features are verified. Users may still opt-in by setting the known env var PYTORCH_JIT_ENABLE_NVFUSER=1. This PR sets this env var for the github actions workflow for ROCm since all current CI hosts are gfx906.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/86369
Approved by: https://github.com/huydhn
