remove feature from frontmatter and commands page

[amtoine]

because Nushell doesn't have features anymore apart from the default pool of commands, i propose to remove the $.feature column from the "commands" page and remove it from the make_docs.nu script as well for it not to appear in the frontmatter of the commands anymore.

Note
i wanted to run nu make_docs.nu and generate the new commands frontmatter sections but the script does not appear to work on 0.94.1 anymore 😕

[hustcer]

Thanks