java: remove hardcoded exclude proto google/rpc/http.proto

[zhumin8]

parity to recent change: googleapis/google-cloud-java#12992

librarian/tool/cmd/migrate/java.go

Lines 500 to 501 in b64ff6c

	case api.Path == "google/rpc":
	api.ExcludedProtos = append(api.ExcludedProtos, "google/rpc/http.proto")