Update onnx-metadata.json

Author: lutzroeder

source/onnx-metadata.json

@@ -15265,6 +15265,12 @@
         "default": 1,
         "description": "Usually each single EPContext associate with a graph partition.But for some case like QNN, it has single EPContext contains all partitions.In that case, the node with ep_cache_context should set main_context=1. Other nodes set main_context=0 and skip ep_cache_context.The path is relative to this Onnx file. Default is 1."
       },
+      {
+        "name": "max_size",
+        "type": "int64",
+        "required": false,
+        "description": "max size in the context. Usage depend on the EP."
+      },
       {
         "name": "notes",
         "type": "string",