fix(empty-states): Remove deprecated button variant and fix spacing

What does this MR do?

Removed deprecated success variant and corrects spacing of buttons in empty states

Before	After

Does this MR meet the acceptance criteria?

Conformity

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• GitLab UI's contributing guidlines.
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• Added the ~"component:*" label(s) if applicable.

Security

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Accessibility

If this MR adds or modifies a component, take a few moments to review the following:

• All actions and functionality can be done with a keyboard.
• Links, buttons, and controls have a visible focus state.
• All content is presented in text or with a text equivalent. For example, alt text for SVG, or aria-label for icons that have meaning or perform actions.
• Changes in a component’s state are announced by a screen reader. For example, changing aria-expanded="false" to aria-expanded="true" when an accordion is expanded.
• Color combinations have sufficient contrast.

Closes #1139 (closed)