correct nn commands in tutorials

[jen-reeve]

Places I noticed it:

• https://docs.nesi.org.nz/Tutorials/Introduction_To_HPC/Resources/#measuring-resource-usage-of-a-finished-job
• https://docs.nesi.org.nz/Tutorials/Introduction_To_HPC/Bash_Shell/#managing-your-data-and-storage-backups-and-quotas

[jen-reeve]

more places:

• https://docs.nesi.org.nz/Tutorials/Introduction_To_HPC/Scaling/#amdahls-law