[PATCH] apn: fix typo on SKT LTE mmsc address

LoL, it's http:// not http//

This fixes MMS on SKT LTE

Change-Id: Ic5506d9e3382b37a4cf78f92326d8759111d5c85
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>