crypto/x509: certificates with AKID don't chain to parents without SKID [1.10 backport]

[gopherbot]

@FiloSottile requested issue #30079 to be considered for backport to the next 1.10 minor release.

@gopherbot please open both backport issues. This is a regression introduced in a minor release

[bcmills]

Per https://golang.org/doc/devel/release.html#policy, now that 1.12 is released, 1.10 is no longer supported.