:%s/^.\{0,5\}// should do the trick. It also handles cases where there are less than 5 characters.
:%s/^.\{0,5\}//
Use the regular expression ^..... to match the first 5 characters of each line. use it in a global substitution:
^.....
:%s/^.....//
As all lines are lined up, you don't need a substitution to solve this problem.Just bring the cursor to the top left position (gg), then:CTRL+vGwlx