FY21Q4 Foundations KR2: Audit and update buttons on SessionsController#new

"FY21-Q4 UX Department: Foundations SubTeam OKR

Objective: Ensure designers have what they need to feel confident utilizing the correct button variant, position, placement, and hierarchy.

KR2: Provide examples of correct button usage by auditing and updating the top 40 most visited pages

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Audit and update buttons found on SessionsController#new. An example of this page can be found here: https://gitlab.com/users/sign_in

Follow the instructions from the parent epic and provide before and after screenshots below:

Before	After