ubuntu.sh: remove unattended-upgrades package

Update apt-get parameter

Signed-off-by: Arthur She <arthur.she@linaro.org>
Change-Id: Ib916f803e1026b093474e859e2b5cf7f16df1b8b
diff --git a/ubuntu.sh b/ubuntu.sh
index 3fa05b4..39c6fa3 100755
--- a/ubuntu.sh
+++ b/ubuntu.sh
@@ -47,7 +47,7 @@
 
 # Disable unattended-upgrade
 systemctl disable unattended-upgrades.service
-apt-get remove unattended-upgrades
+apt-get -y remove unattended-upgrades
 
 sed -i -e 's/#PermitTTY.*/PermitTTY yes/g' /etc/ssh/sshd_config