a11y: 'Download' button is not accessible via keyboard

[nwpappas]

Q&A (please complete the following information)

• OS: all
• Browser: all

Describe the bug you're encountering

'Download' button under 'Try it now' results is not accessible via keyboard.

To reproduce...

Steps to reproduce the behavior:
Using the keyboard...

1. Navigate to https://petstore.swagger.io/#/user/createUsersWithArrayInput
2. Navigate to and active 'Try it out' button
3. Navigate to and active 'Execute' button
4. Navigate to 'Download' button
5. Verify that 'Download' is accessible via keyboard

Expected behavior

'Download' button should be accessible via keyboard.

Screenshots

Additional context or thoughts

'Download' button is not accessible via keyboard, which prevents the users relying on the keyboard to perform their fundamental task.

[char0n]

Addressed in #8974