Fix YAML/JSON confusion

Description

The current documentation to configure SAML authentication instructs to edit the `lms.auth.json` JSON file.
It also warns the user that these changes will be overwritten on the first subsequent ansible run.
But when it comes to suggest how to edit the JSON file, wrong instructions are given: the YAML syntax is used, which won't work for the JSON file.
A seasoned person might not even notice the problem and use the correct syntax anyway, but IMHO it could be very misleading for a beginner.
Sorry for removing everything from the Github issue template. I hope this PR can be useful as it stands.

Status

Assignee

Ned Batchelder

Reporter

Open Source Pull Request Bot

Labels

Contributor Name

Silvio Tomatis

Repo

edx/edx-documentation

Customer

None

Epic Link

None

OSCM Assignee

None

Platform Map Area (Levels 1 & 2)

None

Platform Map Area (Levels 3 & 4)

None

Priority

Unset
Configure