patch 8.1.0758: font number is always one instead of the actual

Problem:    Font number is always one instead of the actual.
Solution:   Use "%d" instead of "1". (Ken Takata)
diff --git a/src/gui_x11.c b/src/gui_x11.c
index 42fb7ca..652bbec 100644
--- a/src/gui_x11.c
+++ b/src/gui_x11.c
@@ -2209,7 +2209,7 @@
 	{
 	    semsg(_("E253: Fontset name: %s"), base_name);
 	    semsg(_("Font0: %s"), font_name[min_font_idx]);
-	    semsg(_("Font1: %s"), font_name[i]);
+	    semsg(_("Font%d: %s"), i, font_name[i]);
 	    semsg(_("Font%d width is not twice that of font0"), i);
 	    semsg(_("Font0 width: %d"),
 				     (int)xfs[min_font_idx]->max_bounds.width);