Disable tests for wasmtime-bench-api (#4395)

Additionally remove the `rlib` crate type so it's possible to build the
API with LTO options if configured (otherwise Cargo ignores LTO
configuration with an `rlib` output since it would hit an error in
rustc)

crates/bench-api/Cargo.toml

@@ -11,8 +11,9 @@ publish = false
 
 [lib]
 name = "wasmtime_bench_api"
-crate-type = ["rlib", "cdylib"]
+crate-type = ["cdylib"]
-# The rlib is only included here so that `cargo test` will run.
+test = false
+doctest = false
 
 [dependencies]
 anyhow = "1.0"