vim: upgrade to 9.0.0021

This fixes the following CVEs:
- CVE-2022-2257
- CVE-2022-2264
- CVE-2022-2284
- CVE-2022-2285
- CVE-2022-2286
- CVE-2022-2287

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>