Fix `type qualifiers ignored on return type` warning (#46668)
Summary:
This fixes following warning:
```
../aten/src/ATen/cpu/vec256/vec256_float_neon.h:262:3: warning: type qualifiers ignored on function return type [-Wignored-qualifiers]
262 | const float operator[](int idx) const {
| ^~~~~
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46668
Reviewed By: seemethere, janeyx99
Differential Revision: D24454206
Pulled By: malfet
fbshipit-source-id: 8ba86a6d6c144f236a76bcef7ce794def7ea131f
