[lookandfeel] Set fixed width for OSD
The complicated calculation for the OSD item's width had the practical effect of always making it PlasmaCore.Units.gridUnit * 15 pixels wide no matter the screen size. So instead of doing all that work, just use that size as a fixed value.
There are no visual changes, but it fixes the following binding loop:
file:///home/nate/kde/usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/osd/Osd.qml:35:15: QML OsdItem: Binding loop detected for property "width"