Minor docs edits to legacy T1 token option

[jeffswartz]

The docs implied that JWT tokens might not be backwards compatible.

Description

Motivation and Context

Clarifies the docs.

How Has This Been Tested?

N/A

Example Output or Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.