tests: 😅 mock consensus height is not updated

[cratelyn]

block::Builder::execute does not update the TestNode<C> height. it should! so that we don't see logs like this when running tests:

  2024-03-12T16:06:19.179075Z TRACE penumbra_mock_consensus::abci: waiting for consensus service
    at crates/test/mock-consensus/src/abci.rs:32
    in penumbra_mock_consensus::abci::end_block
    in penumbra_mock_consensus::block::execute with height: 718, time: 1710259579
    in penumbra_mock_consensus::fast_forward with blocks: 1000, height: 0, fast_forward.blocks: 1000