InĀ WT-7828, ulimit -n 1000000 has been added as the default value was returning 6400 which was too low for the many-coll-test.
In BUILD-13586, the maximum number of file descriptors that can be opened has been set to 1000000 by default, there is no need to call ulimit -n 1000000 in the evergreen.yml file anymore.
the calls to sudo su and ulimit -n can be removed onĀ ubuntu1804-wt-large.