[Send 2][Enhancement] Clicking inside the “Privacy” overlay should dismiss it

[Notes]:

• There should be consistency regarding the dismissal of the overlay considering that the upload complete and Sign in/up overlays are dismissed when clicking inside them.

[Affected versions]:

• Firefox 66.0.3 and up
• Chrome Version 73.0

[Affected Platforms]:

• All Mac
• All Windows
• All Linux

[Steps to reproduce]:

1. Open the browser and navigate to the https://send.firefox.com/ website.
2. Click the “Privacy” button.
3. Click inside the overlay but not on any actionable buttons.

[Expected result]:

• The overlay is dismissed.

[Actual result]:

• The overlay is still displayed.

[Additional Notes]:

• This issue is also reproducible on the https://send2.dev.lcip.org website.
• Attached a screen recording with the issue: