Update TokenCredentialAuthenticationProvider.md

[icyfire0573]

Provided sample at the end wasn't valid for an HTML Head. Modified to suit. Also, there were missing carriage returns that were fixed as part of adding

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Summary

Provided sample at the end wasn't valid for an HTML Head. Modified to suit. Also, there were missing carriage returns that were fixed as part of adding

Motivation

Thing was missing a pair of new lines for correctness / legibility. found it was in an html code block while creating the initial pr; changed to be valid html in general.

Test plan

no tests

Closing issues

Types of changes

syntax

• 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

• I have read the CONTRIBUTING document.
• 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 added tests to cover my changes.
• All new and existing tests passed.