Audit and update buttons on UsersController#show

What does this MR do?

Updates button style and order on user profile pages to conform with Pajamas.

• Move Follow/unfollow buttons far right.
• Make Follow primary confirm. There is no other primary action on the page, and highlighting this also emphasizes the new capability.
• Leave unfollow as default.

Screenshots

Before	After

Does this MR meet the acceptance criteria?

Conformity

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Availability and Testing

N/A

Security

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Related to #273295 (closed)