Add mattsziklay@ and mdehaini@ to windowdecor & freeform OWNERS

Bug: None
Test: None
Flag: EXEMPT updating OWNERS
(cherry picked from https://android-review.googlesource.com/q/commit:15c03f34f8ecf87406fd390307c776e892ad81a8)
Merged-In: I936bc68217d5a67bea98c4c842326707a09b7b6f
Change-Id: I936bc68217d5a67bea98c4c842326707a09b7b6f