Use <button> instead of <a> without `href`
Use <button> instead of <a> without `href`

It is more semantic to use a `<button>` tag in the place of an `<a>`
when there is no other page being linked to. In this circumstance, we're
using JavaScript to present a modal to the user on click.

This change makes the "Upload" and "Rename" buttons appear in the
browser's tab index.

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