Re-align "Register" and "Cancel" buttons in Agent installation modal

What does this MR do and why?

Addressing the button placement issue that pointed out by @anna_vovchenko. It simply swaps the "Register" and "Cancel" buttons from left to right.

Before	After
Peek_2022-01-26_21-28	Peek_2022-01-26_21-27

Closes #351188 (closed)

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