Updated basic authentication details for use without backoffice (CMS 17.4)

[AndyButland]

📋 Description

Updated basic authentication details for use without backoffice, which will be supported from CMS 17.4

📎 Related Issues (if applicable)

umbraco/Umbraco-CMS#22144
umbraco/Umbraco-CMS#22168

✅ Contributor Checklist

I've followed the Umbraco Documentation Style Guide and can confirm that:

• Code blocks are correctly formatted.
• Sentences are short and clear (preferably under 25 words).
• Passive voice and first-person language (“we”, “I”) are avoided.
• Relevant pages are linked.
• All links work and point to the correct resources.
• Screenshots or diagrams are included if useful.
• Any code examples or instructions have been tested.
• Typos, broken links, and broken images are fixed.

Product & Version (if relevant)

CMS 17.4

Deadline (if relevant)

With the release candidate of 17.4, scheduled for Thursday 30th April