Remove oneway designator on contexthub HAL 1.1

According to the linter, the oneway designator should only be used on an
interface that only has oneway methods as it can have implications on
the threading model (among other things).

Bug: 149758462
Test: atest VtsHalContexthubV1_0TargetTest VtsHalContexthubV1_1TargetTest
Change-Id: I969ab2ead1e30f7f4cfa62e292a22833ec5e8471