lualoader: fix the autoboot_delay countdown message

When the timer drops from double to single digits, a spare 'e' is left
on the end of the line as we don't overwrite it. Include an extra space
at the end to account for this and overwrite the leftover character.

PR: 259429

(cherry picked from commit bb4c691299c5d699cea29e18fef96bda1cef13da)