WIP Convert GlDeprecatedButton to GlButton in filtered_search_dropdown.vue

What does this MR do?

Converts GlDeprecatedButton to GlButton in filtered_search_dropdown.vue

Screenshots

Before	After

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

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

Closes #219769 (closed)