Reduce Gauss timing jobs counts from 5 to 3

Some Gauss timing jobs exceed the running time limit of 10h and are automatically killed. This happens especially often for Sim09 nightly slots, and the timing jobs are killed in the last/pre-last iteration, which is a waste. This MR reduces the count of timing jobs from five to three per single PR test, which should not exceed the running time limit, and still be good enough for the purpose of the test.