RavenwoodUtils: remove verifyZeroInteractions wrapper

This is no longer necessary, with the upgrade to Mockito 3 `verifyNoInteractions` is now in the tree.

There are two downsides to having this available:
- The current implementation of MockitoHelper.verifyZeroInteractions  will fail at runtime when on-device tests migrate to Mockito 4+
- Mockito.verifyZeroInteractions has the same behavior as
verify no*More*Interactions. Tests using MockitoHelper.verifyZeroInteractions will therefore observe different behavior on ravenwood and on-device.

Bug: 310268946
Test: n/a, deleted code without usage
Flag: TEST_ONLY
Change-Id: I8e1406a99d748828724b6ac82d2a018a53e725ea