fix(gateway): drop useless cast in SSE keepalive warning log

chrono::milliseconds::count() already returns int64_t on the platforms we
target, matching PRId64. The redundant static_cast triggered -Wuseless-cast
on GCC.

Author: bburda

src/ros2_medkit_gateway/src/http/handlers/sse_fault_handler.cpp

@@ -52,7 +52,7 @@ SSEFaultHandler::SSEFaultHandler(HandlerContext & ctx, std::shared_ptr<SSEClient
   if (keepalive_interval <= std::chrono::milliseconds::zero()) {
     RCLCPP_WARN(HandlerContext::logger(),
                 "Non-positive SSE keepalive override %" PRId64 "ms rejected; using default %ds",
-                static_cast<int64_t>(keepalive_interval.count()), kKeepaliveIntervalSec);
+                keepalive_interval.count(), kKeepaliveIntervalSec);
   }
 
   const auto fault_events_topic = build_fault_manager_events_topic(ctx_.node());