libbinder: remove per-binder wire protocol version

For the RPC project, I had added a version into the binder-level wire
protocol. However, there is no plan to make the on-device wire protocol
backwards compatible, and for RPC, this version needs to be stored with
RpcSession objects, so it is not needed here.

Bug: 182938972
Test: boot, binderStabilityTest
Change-Id: Iad2e7ae77c562690015814ba8d8d439e1befc0b2