Update comment on metrics by level

Co-authored-by: Steve Atherton <steve.atherton@snowflake.com>

fdbserver/VersionedBTree.actor.cpp

@@ -1366,7 +1366,7 @@ struct RedwoodMetrics {
 			}
 		}
 	};
-	// Page levle events
+	// Metrics by level
 	struct Level {
 		struct Counters {
 			unsigned int pageRead;
@@ -9982,4 +9982,4 @@ TEST_CASE(":/redwood/performance/continuousSmapleThroughput") {
 		std::cout << "Time in millisecond: " << elapsed_time_ms << std::endl;
 	}
 	return Void();
-}
+}