fix location of markdown help location

What does this MR do?

Resolves #21208 (closed), and incorrect link to the markdown style guide

Are there points in the code the reviewer needs to double check?

no - this is a simple change

Why was this MR needed?

To provide a better user experience

What are the relevant issue numbers?

#21208 (closed)

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

Milestone changed to %8.11

Added ~149423 regression labels

Enabled an automatic merge when the build for d4e44e90 succeeds

Status changed to merged

mentioned in commit a79ff934

Picked into 8-11-stable, will go into 8.11.1.

Removed ~149423 label

mentioned in commit 9a4e4c01

mentioned in issue #21180 (closed)

mentioned in issue #21409 (closed)