qt: Use quint64 for formatServicesStr

`uint64_t` was causing a build error on some systems, as that type is
not known after including just the Qt headers.

src/qt/guiutil.cpp

@@ -810,7 +810,7 @@ QString formatDurationStr(int secs)
     return strList.join(" ");
 }
 
-QString formatServicesStr(uint64_t mask)
+QString formatServicesStr(quint64 mask)
 {
     QStringList strList;