chore(download-button): fix dynamic style component declaration

[vtsvetkov-splunk]

Issue number:

Summary

styled-components throws error

OpenApiDownloadBtn.tsx:8 The component styled.div with the id of "sc-hIUJlX" has been created dynamically. You may see this warning because you've called styled inside another component. To resolve this only create new StyledComponents outside of any render method and function component.

We should not declare styled components inside a render function

Changes

• styled components have been removed since they are not needed
• Icon moved inside Download button

User experience

No user noticable changes

Checklist

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• I have performed a self-review of this change
• Changes have been tested
• Changes are documented
• PR title follows conventional commit semantics