nedalloc was added to fix the slowness of memory allocator. Here
specifically for the MSys2 build there seems to be a duplication of
USE_NED_ALLOCATOR directive. So this patch intends to remove the
duplicate USE_NED_ALLOCATOR and keeping it only into the MSys2 config
section so it still uses the nedalloc.
Signed-off-by: Harshil-Jani <redacted> Acked-by: Johannes Schindelin <redacted> Signed-off-by: Junio C Hamano <redacted>