docs: Fix code example formatting for virDomainInterfaceAddresses

Adjust the spacing so that the code examples are display in the code/text
box rather than just as paragraph text.

src/libvirt-domain.c

@@ -11533,6 +11533,7 @@ virDomainFSInfoFree(virDomainFSInfoPtr info)
  *       goto cleanup;
  *
  *  ... do something with returned values, for example:
+ *
  *   for (i = 0; i < ifaces_count; i++) {
  *       printf("name: %s", ifaces[i]->name);
  *       if (ifaces[i]->hwaddr)