Update attest-mock digest to a157fc7

Author: oxide-renovate[bot]

Cargo.toml

@@ -372,7 +372,7 @@ assert_matches = "1.5.0"
 assert_cmd = "2.0.17"
 async-bb8-diesel = "0.2"
 async-trait = "0.1.89"
-attest-mock = { git = "https://github.com/oxidecomputer/dice-util", rev = "10952e8d9599b735b85d480af3560a11700e5b64" }
+attest-mock = { git = "https://github.com/oxidecomputer/dice-util", rev = "a157fc75a3a28f45c58b4053b44aa49e8a42fdf0" }
 atomicwrites = "0.4.4"
 authz-macros = { path = "nexus/authz-macros" }
 backoff = { version = "0.4.0", features = [ "tokio" ] }