glcolorscale: fix compiler warning

gstglcolorscale.c(173): warning C4098: 'gst_gl_colorscale_gl_stop': 'void' function returning a value
diff --git a/ext/gl/gstglcolorscale.c b/ext/gl/gstglcolorscale.c
index 88b71ef..74d0168 100644
--- a/ext/gl/gstglcolorscale.c
+++ b/ext/gl/gstglcolorscale.c
@@ -170,7 +170,7 @@
     colorscale->shader = NULL;
   }
 
-  return GST_GL_BASE_FILTER_CLASS (parent_class)->gl_stop (base_filter);
+  GST_GL_BASE_FILTER_CLASS (parent_class)->gl_stop (base_filter);
 }
 
 static gboolean