Remove unused wrk-api-bench dependency (smithy-lang#2331)

* Remove unused `wrk-api-bench` dependency

* Remove benchmark file

Author: jjant

rust-runtime/aws-smithy-http-server/examples/pokemon-service/Cargo.toml

@@ -51,7 +51,6 @@ pokemon-service-server-sdk = { path = "../pokemon-service-server-sdk/" }
 assert_cmd = "2.0"
 home = "0.5"
 serial_test = "0.7.0"
-wrk-api-bench = "0.0.8"
 
 # This dependency is only required for testing the `pokemon-service-tls` program.
 hyper-rustls = { version = "0.23.0", features = ["http2"] }