Fix (graph/standardize): correct check for Mean to AvgPool (#948)

src/brevitas/graph/standardize.py

@@ -59,6 +59,7 @@ def match_node(self, node: Node) -> bool:
         is_adaptive_2d_mean = ((2, 3) in node.args or [2, 3] in node.args or
                                'dim' in node.kwargs and
                                (node.kwargs['dim'] == (2, 3) or node.kwargs['dim'] == [2, 3]))
+        is_adaptive_2d_mean = is_adaptive_2d_mean and not node.kwargs['keepdim']
         return spr and is_adaptive_2d_mean
 
     def move_node_args_to_kwargs(self, node: Node):