Fix comparison, replacing is with ==

[boc-the-git]

/usr/local/lib/python3.13/site-packages/PiicoDev_RFID.py:72: SyntaxWarning: "is" with 'int' literal. Did you mean "=="?
assert max(asw) <= 1 and min(asw) >= 0 and len(asw) is 2, "asw must be a list of 1/0, length=2"

Running with the library on Python 3.13, it gives warnings about the comparison.