[libcxx] [llvm] Remove workarounds for NDK versions before 2017's r16. (PR #148879)

[via llvm-commits]

enh-google wrote:

> Could we move to the new base API since we're touching things anyways? I think it should be as simple as including `<__locale_dir/support/bsd_like.h>`.

where? i was assuming that the
```
#  elif defined(__linux__)
#    include <__locale_dir/support/linux.h>
```
already in the file is the expected path for Android (since we'll already have been taking that anyway!).

https://github.com/llvm/llvm-project/pull/148879