Add mockall feature to api for vault crate (#476)

Running `cargo test` now fails since the vault crate needs mockall. In
CI we always use `--all-features`.

Author: Hinton

crates/bitwarden-vault/Cargo.toml

@@ -57,6 +57,7 @@ wasm-bindgen = { workspace = true, optional = true }
 wasm-bindgen-futures = { workspace = true, optional = true }
 
 [dev-dependencies]
+bitwarden-api-api = { workspace = true, features = ["mockall"] }
 bitwarden-test = { workspace = true }
 tokio = { workspace = true, features = ["rt"] }