UX Polish: Update top right Upload button from Green to Grey

What does this MR do?

Change the Upload designs button background-color: change the class from btn-success to btn-secondary to make it grey

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides

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

Issue #229955 (closed)