[procedures] relax or drop issue linking check.

[dannon]

(Context is #584 (comment))

Now that we're using the new release workflow, I think we can drop the issue linking check. While I think most PRs can/should reference an issue, preferably one created before the PR, they can and should do it in the description. The release notes (not just the latest ones, but past ones) look confusing with all the extra numbers in each line. I think we can link to the PR, which then can link to one (or more) relevant issues for more information, and can still clearly indicate 'fixes #blah' or the like.

Examples:

Old notes:

New notes:

Ideal notes: