Modify var type to match interface

src/core/lib/iomgr/executor/mpmcqueue.h

@@ -119,11 +119,11 @@ class InfLenFIFOQueue : public MPMCQueueInterface {
   CondVar wait_nonempty_;  // Wait on empty queue on get
   int num_waiters_;        // Number of waiters
 
-  Node* queue_head_;           // Head of the queue, remove position
-  Node* queue_tail_;           // End of queue, insert position
-  Atomic<uint64_t> count_{0};  // Number of elements in queue
-  Stats stats_;                // Stats info
-  gpr_timespec busy_time;      // Start time of busy queue
+  Node* queue_head_;       // Head of the queue, remove position
+  Node* queue_tail_;       // End of queue, insert position
+  Atomic<int> count_{0};   // Number of elements in queue
+  Stats stats_;            // Stats info
+  gpr_timespec busy_time;  // Start time of busy queue
 };
 
 }  // namespace grpc_core