fix: use builtin instead of command

[carlosala]

Hey!
Switching from command to builtin. In zsh the keyword command does not resolve to builtin shell commands, only to binaries in the fs.
Thanks!

Fixes #3247

[ljharb]

This seems to break all non-zsh shells, which would make it not the right fix.

[ljharb]

hmm, actually it's when i omit -r that it doesn't do what i expect; with -r it might be correct. I'll keep investigating.

[ljharb]

in ksh, builtin hash -r produces:

builtin: hash: restricted name
builtin: -r: not found

and dash doesn't have builtin at all.

[grous0]

No errors while starting /usr/bin/zsh while these changes made for me.

[ljharb]

Thanks for the contribution; I went with a different approach.