Removes the `target_resmoke_time` and `max_sub_suites` expansions.

Both are dead: nothing in this repo or in mongo-task-generator reads them. Their only consumer was the Python task generator, `buildscripts/task_generation/suite_split.py`. That whole subsystem was deleted in 1b12c649156 ("SERVER-65965 Cleanup old generation tasks code", Aug 2022) when task generation moved to the external `mongo-task-generator`.

`mongo-task-generator` never referenced either name — verified across all commits/branches (git grep over full history).