fix metric name (#222)

Author: jeanbez

.github/workflows/store-metrics.py

@@ -127,7 +127,7 @@
             total_time_file_agg += t
             observed_time_file_agg += t
             obj_close_time_node.append(t)
-        elif 'Sleep time' in line:
+        elif 'Sleep end' in line:
             t = float(line.split(':')[1])
             sleep_time_file_agg += t
             observed_time_file_agg += t