Revert "test-effect-switch: Change one of the pad blocks to and idle probe"

This reverts commit 40fe5dcc84ff2cc7dbe0112d7830a33fd764d4e1.

Using an idle probe here is not ideal because we'll send an EOS event
from the application thread... which might block for quite some time.
Go back to a block probe.

tests/icles/test-effect-switch.c

@@ -110,7 +110,7 @@ pad_probe_cb (GstPad * pad, GstPadProbeInfo * info, gpointer user_data)
 static gboolean
 timeout_cb (gpointer user_data)
 {
-  gst_pad_add_probe (blockpad, GST_PAD_PROBE_TYPE_IDLE,
+  gst_pad_add_probe (blockpad, GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM,
       pad_probe_cb, user_data, NULL);
 
   return TRUE;