Remove a couple of CompletableFuture methods from CorePlatformApi

CompletableFuture.{completeOnTimeout,failedFuture} are already public
and in api/current.txt so do not need CorePlatformApi annotations.

(cherry picked from commit ce13570ebb0dc152faf375188fabeb15141cc4ce)

Bug: 185153775
Test: m
Merged-In: I9dc49e04e2345d9ae59cf209dcf343f835c7ec71
Change-Id: I164792574e8dcb4658bc2a26c277787484a119b7
3 files changed