Freeze 'current' matrix as '5'.

To signify this as being ready for release.

Bug: 147496715
Test: build & boot cf (which is at target-level 5)
Change-Id: I7bb9d561506849bac2353d9356a6580f6e2393ab
(cherry picked from commit 0e0665efec1b61ef329a370b9483937b7ce9ac9f)
Merged-In: I7bb9d561506849bac2353d9356a6580f6e2393ab