SystemUI: Trim whitespace on a string resource

The floating_mode_blacklisted_app string resource has seemingly
unnecessary whitespace. This commit removes that.

Change-Id: I8f24778395912a684e99d9e847d544db9335b114
Merge "SystemUI: Trim whitespace on a string resource" into kitkat

Change-Id: Id58668b1539bbccf4e4c523c80f481cbc95100e7