[transformer benchmark] relax tolerance in sdp.py (#101965)
Summary:
Otherwise we get
```
Traceback (most recent call last):
File "<string>", line 49, in <module>
File "<string>", line 47, in __run
File "/usr/local/fbcode/platform010/lib/python3.8/runpy.py", line 194, in _run_module_as_main
return _run_code(code, main_globals, None,
File "/usr/local/fbcode/platform010/lib/python3.8/runpy.py", line 87, in _run_code
exec(code, run_globals)
File "/data/users/jongsoo/fbsource/buck-out/v2/gen/fbcode/ef4169ac7f95fb74/caffe2/benchmarks/transformer/__sdp__/sdp#link-tree/caffe2/benchmarks/transformer/sdp.py", line 346, in <module>
main(save_path)
File "/data/users/jongsoo/fbsource/buck-out/v2/gen/fbcode/ef4169ac7f95fb74/caffe2/benchmarks/transformer/__sdp__/sdp#link-tree/caffe2/benchmarks/transformer/sdp.py", line 328, in main
experiment = run_single_experiment(experiment_config)
File "/data/users/jongsoo/fbsource/buck-out/v2/gen/fbcode/ef4169ac7f95fb74/caffe2/benchmarks/transformer/__sdp__/sdp#link-tree/caffe2/benchmarks/transformer/sdp.py", line 229, in run_single_experiment
assert_close_tensors(nn_mha_output, composite_mha_output)
File "/data/users/jongsoo/fbsource/buck-out/v2/gen/fbcode/ef4169ac7f95fb74/caffe2/benchmarks/transformer/__sdp__/sdp#link-tree/caffe2/benchmarks/transformer/sdp.py", line 196, in assert_close_tensors
assert torch.allclose(a, b, atol=1e-3, rtol=1e-3)
AssertionError
```
Test Plan: buck run mode/dev-nosan //caffe2/benchmarks/transformer:sdp
Differential Revision: D45843836
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101965
Approved by: https://github.com/drisspg
