Add metadata field to memory update schema (#3115)

docs/openapi.json

@@ -1699,6 +1699,10 @@
 									"text": {
 										"type": "string",
 										"description": "The updated text content of the memory"
+									},
+									"metadata": {
+										"type": "object",
+										"description": "Additional metadata associated with the memory"
 									}
 								}
 							}