vim: fix CVE-2021-3778

vim is vulnerable to Heap-based Buffer Overflow

reference:
https://github.com/vim/vim/commit/65b605665997fad54ef39a93199e305af2fe4d7f


(From OE-Core rev: 494929c4cec21712884e13172c37efad7c908411)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>