sample/sampled: remove ipc.LeafDispatcher
sample/sampled: remove ipc.LeafDispatcher

The corresponding core change is in go/vcl/1323

Change-Id: I812a2c43d4087c1c01a5058ea53bd34b8ef9743c
MultiPart: 4/4

vanadium/browser,vanadium/browser,vanadium/browser,vanadium/browser