instruments.xml: Make drum names refer to instrument not sound

Run share/instruments/update_instruments_xml.py to fetch the latest
version of the online spreadsheet. In this version, drum names have
been updated to refer to the actual drum being notated rather than
the MIDI sound used for playback. The MIDI sound is often a substitute
because the actual instrument sound is not available.

Drum names are displayed as tooltips in the drumset palette, which
appears when you enter notes on a percussion staff. They are also
displayed in the "Edit Drumset" dialog available from that palette.