core: Remove unused strings

These are from CAF but they are no longer used and generate aapt warnings.
They should have been removed in this http://review.cyanogenmod.org/60253

Change-Id: I285a3767dff0b5ccd01a2a9c9863377f11060f81
MSIM: Expanded StatusBar: Show SIM slot number

Change-Id: I5c9ba33bfd564ba5301072ba1ef8c33640943710