chore: Remove direct dependency to multihash -- use cid re-export instead

[jsantell]

multihash is used by many of our dependencies (cid, libipld-, libp2p) and there were some breaking changes in 0.19 (https://github.com/subconsciousnetwork/noosphere/pull/824) -- all of our usage of multihash is via cid::multihash, except in the single usage in an example where we use it directly. Continue using the version provided by cid (in sync with `libipld-`)., as this is used throughout many dependencies, it's more important staying in sync than updating to the latest.

[github-actions[bot]]

Test flake analysis

status	platform	features	toolchain
🟢	macos-13	test-kubo,headers,rocksdb	stable
🟡	macos-13	test-kubo,headers	stable
🟡	ubuntu-latest	test-kubo,headers	stable
🟢	ubuntu-latest	test-kubo,headers	nightly
🟢	windows-latest	test-kubo,headers	stable
🟢	ubuntu-latest	test-kubo,headers,rocksdb	stable

Flake summary for macos-13, test-kubo,headers, stable

     Summary [ 119.925s] 209 tests run: 209 passed (2 flaky), 2 skipped
   FLAKY 2/5 [  10.124s] noosphere::distributed_basic synchronize_petnames_as_they_are_added_and_removed
   FLAKY 2/5 [  43.516s] noosphere::distributed_stress latency::clients_can_sync_when_there_is_a_lot_of_content

Flake summary for ubuntu-latest, test-kubo,headers, stable

     Summary [  42.808s] 209 tests run: 209 passed (1 flaky), 2 skipped
   FLAKY 2/5 [   1.065s] noosphere-ns dht::node::test::test_dhtnode_bootstrap