Use tobytes instead of tostring

[Inokinoki]

array.array.tostring() has been removed in 3.9 and deprecated earlier.

Executing the script gives me:

Traceback (most recent call last):
  File ".../shofel2_linux/./shofel2.py", line 247, in <module>
    rcm.pwn()
  File ".../shofel2_linux/./shofel2.py", line 210, in pwn
    data = s.ep1_read(4096).tostring()
AttributeError: 'array.array' object has no attribute 'tostring'