[libc++] Remove a duplicated definition of _LIBCPP_NOINLINE (#79114)

I failed to delete the old definition as a part of
llvm/llvm-project#73838.

NOKEYCHECK=True
GitOrigin-RevId: 9629c73aeb4609f58aa9edb0b87d18dd9e8fecc0

Author: gribozavr

include/__config

@@ -1235,12 +1235,6 @@ __sanitizer_verify_double_ended_contiguous_container(const void*, const void*, c
 #    define _LIBCPP_CONSTINIT
 #  endif
 
-#  if __has_attribute(__noinline__)
-#    define _LIBCPP_NOINLINE __attribute__((__noinline__))
-#  else
-#    define _LIBCPP_NOINLINE
-#  endif
-
 #  if defined(__CUDACC__) || defined(__CUDA_ARCH__) || defined(__CUDA_LIBDEVICE__)
 // The CUDA SDK contains an unfortunate definition for the __noinline__ macro,
 // which breaks the regular __attribute__((__noinline__)) syntax. Therefore,