SERVER-108257 lowered the default maximum number of spill WT sessions from 33,000 to 1,024, making it a separate parameter from the maximum number of main WT sessions. In order to ensure that queries can't spuriously fail just because they happen to spill, we should increase the default maximum number of spill WT sessions back to 33,000 and keep it in sync with the maximum number of main WT sessions. This effectively reverts SERVER-108257.