Bump KylovKit compat to include 0.8

[leburgel]

Hi,
I would like to try out some of the features introduced in KrylovKit.jl v0.8 in a project that depends on QuantumOptics.jl, but I'm getting a compat issue due to KylovKit.jl being restricted to v0.6 here. Is there any reason not to bump the KrylovKit compat to v0.8 (#397 )? I saw in #385 that there was a concern with LinearSolve, but it seems its KrylovKit.jl compat was already set to v0.8 so this should not be a problem.

[david-pl]

@Krastanov do you see any reason this should cause problems? Otherwise, I'd just go ahead and merge the CompatHelper PRs.

[Krastanov]

I am in favor! Thanks for looking into it!

[david-pl]

Alright, the latest release has the updated compat.