virt-cat, virt-ls, virt-edit: Fix typo in documentation.

This fixes the following:
 commit aad3c467fb47d3aa0720624c20561cd8eb34072b
 commit de5e7331afbb83ffac509e899851e791191922b3
 commit 86706907af1adea96820ec2c5aa4222fcc4065b0