gitian deps-win32.yml needs psmisc package for killall to end the build

gitian build of contrib/gitian-descriptors/deps-win32.yml fails with the following and gets stuck.  This patch adds psmisc which contains killall.  The build is allowed to complete when these processes are dead.

  adding: miniupnpc/upnpcommands.h (deflated 76%)
  adding: miniupnpc/upnperrors.h (deflated 38%)
  adding: miniupnpc/upnpreplyparse.h (deflated 58%)
+ killall wineserver services.exe explorer.exe winedevice.exe
bash: line 59: killall: command not found