Fix help text on /admin/reports/updates/settings about permission added in #332796

Problem/Motivation

#332796: Add permissions to the update.module to hide warnings → was released before the release managers had signed off. @xjm pointed out that the help text at /admin/reports/updates/settings which mentions the new permission needs help.

We probably want to wait to do this until we decide the final name / description of the permission itself, so postponed on 🐛 Fix the label and description of the new "view update notifications" permission Needs review

Steps to reproduce

Proposed resolution

Remaining tasks

1. Finalize and commit 🐛 Fix the label and description of the new "view update notifications" permission Needs review
2. Implement fixes to help text in core/modules/update/src/UpdateSettingsForm.php
3. Reviews / refinements.
4. Usability review.
5. Release manager review.

User interface changes

TBD.

API changes

Data model changes

Release notes snippet