Fix PySnooper 2 buggy commit id

[h4iku]

The correct buggy id of PySnooper 2 is different: cool-RR/PySnooper@814abc3
Current one causes both the buggy and fixed versions to error out:

==================================== ERRORS ====================================
___________________ ERROR collecting tests/test_pysnooper.py ___________________
tests/test_pysnooper.py:11: in <module>
    from pysnooper.utils import truncate
pysnooper/__init__.py:20: in <module>
    from .tracer import Tracer as snoop
pysnooper/tracer.py:18: in <module>
    if pycompat.PY2:
E   AttributeError: module 'pysnooper.pycompat' has no attribute 'PY2'
=========================== short test summary info ============================
ERROR tests/test_pysnooper.py - AttributeError: module 'pysnooper.pycompat' h...
3 warnings, 1 error in 1.40s