Follow up update for streaming event UI

Background

This is the follow-up discussion of the comment.

Changes needed:

1. Remove the according and change it to a title.
2. Adjust the font-size because of the update of the new fluid-type implementation

Implementation steps

• Update font sizes of the destination count, Custom HTTP headers (optional) header, and Event filtering (optional) header
• Remove "Filter by stream event" accordion and use label instead (with label and listbox indented)
• Update specs accordingly

Verification steps

• Go to issue-reproduce audit event streams
• Verify that the destination count header is an h4 element
• Expand the destination by clicking its url
• Verify that you can directly use the "Filter by audit event type" dropdown, you don't need to first expand an accordion like before.