Terraform bug is fixed -> Doc update

[stephanlindauer]

The terraform bug, mentioned in the README.md is fixed and should probably not be mentioned in the README.md anymore but rather kops should have a dependency to terraform >= 7.0

More info regarding the bug:
hashicorp/terraform#2143

[justinsb]

Do you know of any way we can enforce that a terraform manifest is only for version >= X? I worry that we have to keep advertising it because most people won't be on 0.7 for the while, and terraform fails silently for < 0.7.

I agree we can put the workaround into a child page though, but at least for now we probably have to keep the notice pretty prominent.

[justinsb]

Going to rejig the docs, and hopefully everyone will update quickly. But AFAICT there's not version annotation in 0.7, so I can't remove it entirely:

hashicorp/terraform#4092
hashicorp/terraform#1400

I'm a little wary of the trick in hashicorp/terraform#4092 (comment)

[justinsb]

Moving further work on this (e.g. locking to a particular version) to the backlog

[chrislovecnm]

We specify version and the docs are updated