devel/libunwind: Clean up unwind.h patch

- Bump PORTREVISION for package change

unwind.h was installed to /usr/include in mid-February, 2022.
Since all supported FreeBSD releases have /usr/include/unwind.h, this patch is
no longer needed.

Reviewed by:	tijl
Reference:	https://cgit.freebsd.org/ports/commit/?id=975a5c1057579603c4041c2b8e3ac0933ea0eb89