gobject/performance: drop wrong additional warm up during test run

For the test, we actually care to find the fastest test run (and take
"min_elapsed"). That is useful, because that is the run where we
possibly have the least interference from external factors, it was the
run where the CPU solved the problem as fast as it could.

As such, we should not reject the first 5% as additional warm up. If the
first 5% are slower (and part of "warmup"), then they are anyway not
considered. If there is a the fastest run in the first 5 percent, then
we want to take that.

Also note, that the calculation of "avg_elapsed" was wrong, since it
divided by the full "num_rounds" while only summing 95% of the runs.
This is fixed too by now considering all runs.

Fixes: 282d536fd229 ('tests/performance: ensure to always warm up for 2 seconds')

gobject/tests/performance/performance.c

@@ -189,12 +189,6 @@ run_test (PerformanceTest *test)
       g_timer_stop (timer);
       test->finish (test, data);
 
-      if (i < num_rounds / 20)
-        {
-          /* The first 5% are additional warm up. Ignore. */
-          continue;
-        }
-
       elapsed = g_timer_elapsed (timer, NULL);
 
       min_elapsed = MIN (min_elapsed, elapsed);