fix: wrong first sumbit time value in test

test/workloads/SABjson/many_preceding.SABjson

@@ -84,7 +84,7 @@
         },
         {
             "id": 6,
-            "first_submit_time": 2000.0,
+            "first_submit_time": 4000.0,
             "preceding_sessions": [1,2,3,4,5],
             "thinking_time_after_preceding_session": [1000,1000,1000,1000,1000],
             "nb_jobs": 1,