New review comment by paper42 on void-packages repository

https://github.com/void-linux/void-packages/pull/41089#discussion_r1051047851

Comment:
there is no point in setting a variable when it's only going to be used once in the code
```suggestion
	for shell in bash fish zsh; do
		vtargetrun ${DESTDIR}/usr/bin/glab completion -s ${shell} > glab.${shell}
		vcompletion glab.${shell} ${shell}
	done
```