Remove redundant collectgarbage() calls from scripts

Since 8112d6472e garbage is automatically collected
after running a Lua GUI script.

share/scripts/_vamp_note_example.lua

@@ -61,8 +61,4 @@ function factory () return function ()
 	::out::
 	-- hide modal progress dialog and destroy it
 	pdialog:done ();
-	pdialog = nil
-	vamp = nil;
-	collectgarbage ()
-
 end end