vim: upgrade to 8.2 patch 3752

There's a fairly constant flow of CVEs being fixed in Vim, which are
getting increasing non-trivial to backport.

Instead of trying to backport (and potentially introduce more bugs), or
just ignoring them entirely, upgrade vim to the latest patch in the hope
that vim 8.3 will be released before we release Kirkstone.

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