ewah: delete unused ewah_read_mmap_native declaration

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ewah/ewok.h

@@ -100,7 +100,6 @@ int ewah_serialize_native(struct ewah_bitmap *self, int fd);
 
 int ewah_deserialize(struct ewah_bitmap *self, int fd);
 int ewah_read_mmap(struct ewah_bitmap *self, const void *map, size_t len);
-int ewah_read_mmap_native(struct ewah_bitmap *self, void *map, size_t len);
 
 uint32_t ewah_checksum(struct ewah_bitmap *self);