[DOCS] Port extensions command (#26863)

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Author: tsavina

docs/articles_en/assets/snippets/ov_extensions.py

@@ -47,7 +47,7 @@ def conversion(node):
 #! [py_frontend_extension_aten_hardtanh]
 import torch
 from openvino.frontend import ConversionExtension, NodeContext
-from openvino.tools.mo import convert_model
+from openvino import convert_model
 
 
 class HardTanh(torch.nn.Module):
@@ -69,5 +69,5 @@ def convert_hardtanh(node: NodeContext):
 
 model = HardTanh(min_val=0.1, max_val=2.0)
 hardtanh_ext = ConversionExtension("aten::hardtanh", convert_hardtanh)
-ov_model = convert_model(input_model=model, extensions=[hardtanh_ext])
+ov_model = convert_model(input_model=model, extension=[hardtanh_ext])
 #! [py_frontend_extension_aten_hardtanh]