[pytorch][te][easy] Remove KernelScope from fusion pass tests (#47952)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47952
We don't actually generate a TE kernel so no need to use the
arena-allocation guard.
Test Plan:
```
buck test //caffe2/test/cpp/tensorexpr -- FuserPass
```
Reviewed By: ZolotukhinM
Differential Revision: D24967107
fbshipit-source-id: 302f65b2fcff704079e8b51b942b7b3baff95585
