virConnect: Update comment for @privateData

This member allows us to store a pointer to some private data.
However, the comment says it's used in both domain driver and
network driver. Well, it is not. It's just one pointer and domain
driver uses it directly. Network driver has a global driver
variable. Update the comment to not confuse others.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/datatypes.h

@@ -472,8 +472,8 @@ struct _virConnect {
     virSecretDriverPtr secretDriver;
     virNWFilterDriverPtr nwfilterDriver;
 
-    /* Private data pointer which can be used by driver and
-     * network driver as they wish.
+    /* Private data pointer which can be used by domain driver as
+     * it pleases.
      * NB: 'private' is a reserved word in C++.
      */
     void *            privateData;