fix the StartupWMClass for bitoin-qt, so gnome-shell can recognize it

contrib/debian/bitcoin-qt.desktop

@@ -1,5 +1,5 @@
 [Desktop Entry]
-Encoding=UTF-8
+Version=1.0
 Name=Bitcoin Core
 Comment=Connect to the Bitcoin P2P Network
 Comment[de]=Verbinde mit dem Bitcoin peer-to-peer Netzwerk
@@ -11,3 +11,4 @@ Type=Application
 Icon=bitcoin128
 MimeType=x-scheme-handler/bitcoin;
 Categories=Office;Finance;
+StartupWMClass=Bitcoin-qt