Migrates the expand button in reports to gitlab UI

What does this MR do?

This migrates the pesky "Expand" button in MR widget reports to use the <gl-button> component.

Screenshots (strongly suggested)

Before	After

Does this MR meet the acceptance criteria?

Conformity

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• [-] Documentation (if required)
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done