CI: change ubuntu cross exe_wrapper to un-suffixed wine

wine64 used to be the way to run a 64-bit wineserver. It was removed due
to https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1029536 despite
that bug report being about a bug in an unrelated symlink -- apparently
there's no recommended solution to starting a specific bitness of wine
on demand. The automagic `wine` I believe creates a wineprefix with
both, which is... probably not exactly efficient here? But whatever, not
worth fighting it. Just get this more or less working again.

cross/linux-mingw-w64-64bit.txt

@@ -6,7 +6,7 @@ ar = '/usr/bin/x86_64-w64-mingw32-ar'
 strip = '/usr/bin/x86_64-w64-mingw32-strip'
 pkgconfig = '/usr/bin/x86_64-w64-mingw32-pkg-config'
 windres = '/usr/bin/x86_64-w64-mingw32-windres'
-exe_wrapper = 'wine64'
+exe_wrapper = 'wine'
 cmake = '/usr/bin/cmake'
 
 [properties]