fix(tests): remove stale _dd.compute_stats:1 assertion from logs integration test (#1136)

https://datadoghq.atlassian.net/browse/SVLS-8767

## Summary
- `_dd.compute_stats` was moved from general log tags to trace-only
payloads in commit `55659d93`
- The `test_logs` integration test mock still required
`_dd.compute_stats:1` in the log body
- The mock never matched → httpmock returned non-2xx → `Flusher::send()`
retried infinitely → test hung forever

## Test plan
- [ ] `cargo test --test logs_integration_test test_logs` passes and
completes in < 1s

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: litianningdatadog

bottlecap/tests/logs_integration_test.rs

@@ -22,7 +22,6 @@ async fn test_logs() {
     // protobuf is using hashmap, can't set a btreemap to have sorted keys. Using multiple regexp since
     // Can't do look around since -> error: look-around, including look-ahead and look-behind, is not supported
     let regexp_message = r#"[{"message":{"message":"START RequestId: 459921b5-681c-4a96-beb0-81e0aa586026 Version: $LATEST","lambda":{"arn":"test-arn","request_id":"459921b5-681c-4a96-beb0-81e0aa586026"},"timestamp":1666361103165,"status":"info"},"hostname":"test-arn","service":"","#;
-    let regexp_compute_state = r#"_dd.compute_stats:1"#;
     let regexp_arch = format!(r#"architecture:{}"#, arch);
     let regexp_function_arn = r#"function_arn:test-arn"#;
     let regexp_extension_version = r#"dd_extension_version"#;
@@ -34,7 +33,6 @@ async fn test_logs() {
             .header("DD-API-KEY", dd_api_key)
             .header("Content-Type", "application/json")
             .body_contains(regexp_message)
-            .body_contains(regexp_compute_state)
             .body_contains(regexp_arch)
             .body_contains(regexp_function_arn)
             .body_contains(regexp_extension_version);