Drop unused global var WINEASIO_PREFIX

It was mis-formatted anyway. Looks like a
copy-paste from wineasio which is broken in the
exact same way[1].

[1] 638ce56a7f/gui/settings.py (L41)

src/cadence.py

@@ -113,8 +113,6 @@ XDG_APPLICATIONS_PATH = [
     "/usr/local/share/applications"
 ]
 
-WINEASIO_PREFIX = "HKEY_CURRENT_USER\Software\Wine\WineASIO"
-
 # ---------------------------------------------------------------------
 
 global jackClientIdALSA, jackClientIdPulse