Add maxTargetSDK equals P for UnsupportedAppUsage of sCached

We figured out this non-SDK API is mainly used for a previous
memory workaround. Since the bug was fixed, this API is not
allowed to access.

Bug: 123768439
Test: N/A
Change-Id: Ib04bf7e630aee0896c8432aa9c5b794440ea7a2d