[gtk] testpopup: Fix GtkEventControllerMotion::motion callback signature

[Timm Bäder <baedert src gnome org>]

commit 45b909f2c5fd43fbb9a2d6d99edf509c91e954d6
Author: Timm Bäder <mail baedert org>
Date:   Thu Nov 8 05:19:48 2018 +0100

    testpopup: Fix GtkEventControllerMotion::motion callback signature

 tests/testpopup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/tests/testpopup.c b/tests/testpopup.c
index 085d08ca2f..b496fe5eae 100644
--- a/tests/testpopup.c
+++ b/tests/testpopup.c
@@ -11,7 +11,7 @@ draw_popup (GtkDrawingArea  *da,
   cairo_paint (cr);
 }
 
-static gboolean
+static void
 place_popup (GtkEventControllerMotion *motion,
              gdouble                   x,
              gdouble                   y,