Grammatical fix. Replace 'insure' with 'ensure'.

doc/html/accounting.shtml

doc/html/api.shtml

doc/html/bluegene.shtml

doc/html/contributor.shtml

doc/html/cray_alps.shtml

doc/html/download.shtml

doc/html/faq.shtml

doc/html/gres.shtml

doc/html/heterogeneous_jobs.shtml

doc/html/job_container_plugins.shtml

doc/html/node_features_plugins.shtml

doc/html/power_save.shtml

doc/html/proctrack_plugins.shtml

doc/html/quickstart.shtml

doc/html/quickstart_admin.shtml

doc/html/reservations.shtml

doc/man/man1/salloc.1

doc/man/man1/sbatch.1

doc/man/man1/srun.1

doc/man/man1/strigger.1