Issue #3414263 by quietone, andypost: Change help headings for WCAG 2.0

core/modules/action/action.module

core/modules/announcements_feed/announcements_feed.module

core/modules/automated_cron/automated_cron.module

core/modules/ban/ban.module

core/modules/basic_auth/basic_auth.module

core/modules/big_pipe/big_pipe.module

core/modules/block/block.module

core/modules/block_content/block_content.module

core/modules/book/book.module

core/modules/breakpoint/breakpoint.module

core/modules/ckeditor5/ckeditor5.module

core/modules/comment/comment.module

core/modules/config/config.module

core/modules/config_translation/config_translation.module

core/modules/contact/contact.module

core/modules/content_moderation/content_moderation.module

core/modules/content_translation/content_translation.module

core/modules/contextual/contextual.module

core/modules/datetime/datetime.module

core/modules/datetime_range/datetime_range.module