Resets the future plan to sequential processing.
Examples
if (FALSE) { # \dontrun{
# Setup parallel processing
old_plan <- setup_llm_parallel(workers = 2)
# Do some parallel work...
# Reset to sequential
reset_llm_parallel(verbose = TRUE)
# Optionally restore the specific old_plan if it was non-sequential
# future::plan(old_plan)
} # }