docs: clarify automation in release workflow

[inge4pres]

Motivation/summary

During the 8.15 release cycle we noticed some differences between what documented as needed and the available tooling for release. This Pr is an attempt to clarify what's documented.

[mergify[bot]]

This pull request does not have a backport label. Could you fix it @inge4pres? 🙏 To fixup this pull request, you need to add the backport labels for the needed branches, such as:

• backport-7.17 is the label to automatically backport to the 7.17 branch.
• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.

NOTE: backport-skip has been added to this pull request.

[carsonip]

@inge4pres Do the changes still apply? Do you want to hand this PR over to @1pkg ?

[inge4pres]

Amended the phrasing as suggested, trying to see how the preview renders the important block

[inge4pres]

how the preview renders the important block

works with latest commit