Final answer:
Remove the line 'for i in range(8):' to fix the program.
Step-by-step explanation:
The incorrect line of code that should be removed to make the program do what it's supposed to is:
for i in range(8):
Because this line of code is causing the function to draw the square 8 times in a row without moving the turtle forward. To fix this, you should remove this line of code and simply call the draw_square() function once.