sandbox: Drop the 'starting...' message

This message is annoying since it is only useful for testing. Drop it and
update the test to cope.

Signed-off-by: Simon Glass <sjg@chromium.org>

test/py/tests/test_log.py

@@ -45,5 +45,4 @@ def test_log_dropped(u_boot_console):
     cons = u_boot_console
     cons.restart_uboot()
     output = cons.get_spawn_output().replace('\r', '')
-    assert 'sandbox: starting...' in output
     assert (not 'debug: main' in output)