CLN: remove __metaclass__

Author: topper-123

pandas/core/computation/engines.py

@@ -35,12 +35,9 @@ def _check_ne_builtin_clash(expr):
                                      .format(expr=expr, s=s))
 
 
-class AbstractEngine:
-
+class AbstractEngine(metaclass=abc.ABCMeta):
     """Object serving as a base class for all engines."""
 
-    __metaclass__ = abc.ABCMeta
-
     has_neg_frac = False
 
     def __init__(self, expr):