Go into iFile > System > Library> Core Services > Springboard.app > (your language) > Springboard.strings, BACKUP YOUR SPRINGBOARD.STRINGS SOMEWHERE SAFE, open in Text Editor, search/scroll for "enter" and you'll see something like "ENTER_PASSCODE" = "Enter Passcode". Remove the text on the right to "ENTER_PASSCODE" = "". Repeat for "Wrong Passcode" and "try again".