Fixed the AuthenticationProviderInterface alignment
minor #12917 [2.3] [Security] Fixed The AuthenticationProviderInterface Alignment (GrahamCampbell)

This PR was merged into the 2.3 branch.

Discussion
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[2.3] [Security] Fixed The AuthenticationProviderInterface Alignment

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        | N/A

##### This pull request fixes the AuthenticationProviderInterface alignment.

Everything was indented by one too many spaces.

Commits
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1270327 Fixed the AuthenticationProviderInterface alignment