[reboot] Add favourite screen has confusing non-icon

[Alan Pope 🍺🐧🐱 🦄]

Users have been confused by the icon in the add favourite screen.

Type in a calculation, swipe left and tap the star, this should add a favourite.

In this screenshot
http://people.canonical.com/~alan/screenshots/device-2015-03-24-140512.png

Next to the date there is an "enter key" icon. It feels like you should be able to tap this. However if you do so, you end up in this state:-

http://people.canonical.com/~alan/screenshots/device-2015-03-24-141001.png

The favourite wasn't added. If you go back, you end up back at:-

http://people.canonical.com/~alan/screenshots/device-2015-03-24-141026.png

Which has no OSK, but _has_ an enter "button" which confuses you more because you can then flip-flop between the two states above.

I propose we remove the enter icon on that line, and rely (as we should) on the enter key in the OSK

[Bartosz Kosiorek (gang65)]

The "enter key" icon should be displayed only on Desktop, because without OSK you don't have possibility to confirm Favourite caption.

[Ubuntu Phone Apps Jenkins Bot (ubuntu-phone-apps-jenkins-bot)]

Fix committed into lp:ubuntu-calculator-app/reboot at revision 145, scheduled for release in ubuntu-calculator-app, milestone Unknown