Fix ENABLE_RECORD_KERNEL_FUNCTION_DTYPE build (#65370)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65370
Forgot a wrapping 'namespace at' here! And no contbuilds to test it.
ghstack-source-id: 138565579
Test Plan:
```
buck build --show-output -c pt.disable_per_op_profiling=0 -c pt.enable_record_kernel_dtype=1 -c pt.has_backtraces=1 fbsource//xplat/caffe2/fb/model_tracer:model_tracer
```
Reviewed By: JacobSzwejbka
Differential Revision: D31065923
fbshipit-source-id: ed4563fbd8f3c29f6b10ac8999c9010bd4359c97
