Remove system-out output in sponge.xml
Remove system-out output in sponge.xml

The output bloats the XML and is reundant to the
separate log file.

Change-Id: I9a19e8b7bd7b67e83c05135bf6e82925beb7efe3

GoogleCloudPlatform/iap-desktop,GoogleCloudPlatform/iap-desktop