The file size should not (only) be displayed in the Download button, to reduce the temptation for misclicks

Jeff M. told me that he frequently clicks the Download button instead of the Upload button when he tries to share a profile, by accident. This happens when he wants to minimize the amount of uploaded data by tweaking the profile contents with the checkboxes. After clicking the checkboxes, the file size updates and is displayed in the Download button. This seems to make it tempting to click the Download button afterwards.

However, the file size isn't really specific to Download, it applies just as much to Upload. So it probably shouldn't be inside the button at all.


┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-425)