Accessibility: Update other `FeedbackPrompt`

Created by: umpox

Description

Found through a11y audit: https://github.com/sourcegraph/sourcegraph/issues/34413

Fixes:

• Aria hides unnecessary images, where we already have an aria-label set through our radio buttons
• Adds labels to important images, so screen readers can "Close" the prompt and can understand the "Success" state
• Labels the feedback prompt title with the text area, so users understand some context of the prompt

Test plan

Tested locally with a screen reader

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.