fix: correct base class name to match autogen output

Rename _Huaweicloud to _HuaweiCloud in __init__.py to match
the import reference generated by autogen.sh, consistent with
the AlibabaCloud provider naming convention (_AlibabaCloud).

diagrams/huaweicloud/__init__.py

@@ -5,7 +5,7 @@ Huaweicloud provides a set of services for Huawei Cloud provider.
 from diagrams import Node
 
 
-class _Huaweicloud(Node):
+class _HuaweiCloud(Node):
     _provider = "huaweicloud"
     _icon_dir = "resources/huaweicloud"