Only set the comment when persist_docs.relation is set

[Fokko]

Overview

I accidentally changed default behavior in #317

Resolves #343

Checked that it only sets the comment when:

{{ config(
    ...
    persist_docs={"relation": true}
) }}

And with the following configuration it won't set the comment:

{{ config(
    ...
    persist_docs={"relation": false}
) }}

{{ config(
    ...
) }}

Checklist

• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• README.md updated and added information about my change
• I have run changie new to create a changelog entry

[Fokko]

Gentle ping @damian3031

[damian3031]

@Fokko I added tests for this change

[damian3031]

Gentle ping @Fokko 🙂 Please adjust to (or comment on) the requested changes, and PR is good to merge

[Fokko]

@damian3031 Sorry for not replying earlier, thanks for adding tests, and the changes look good 👍🏻

[damian3031]

@Fokko thanks! Could you squash these 2 new commits into the first one? (this one 2432b48 (#344))

[damian3031]

@Fokko thanks for your contribution!

[alaturqua]

@Fokko Thank you for fixing this.

When is the next release actually?

[damian3031]

@alaturqua It has just been released in 1.6.2!

[Fokko]

Thanks @damian3031 for shepherding this, and sorry @alaturqua for breaking this