element-maker: Avoid leaking copy of caps object

gst_pad_get_pad_template_caps() returns a reference which is unreferenced,
so creating a copy using gst_caps_copy() results in a reference leak.

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=734539

tools/element-templates/srcpad

@@ -76,7 +76,7 @@ gst_replace_src_getcaps (GstPad *pad)
 
   GST_DEBUG_OBJECT(replace, "getcaps");
 
-  caps = gst_caps_copy (gst_pad_get_pad_template_caps (pad));
+  caps = gst_pad_get_pad_template_caps (pad);
 
   gst_object_unref (replace);
   return caps;