Add compatibility for mypy 0.960

Tested on
python/mypy@128661c.
Also reported as python/mypy#12861.

Author: rouge8

mypy_nonfloat_decimal/mypy_nonfloat_decimal.py

@@ -29,7 +29,7 @@ def get_function_hook(
         :param fullname: full name of the type to consider
         :return: callback for specific type call
         """
-        if fullname == "decimal.Decimal":
+        if fullname in ("_decimal.Decimal", "decimal.Decimal"):
             return analyze_decimal_call
         return None