[doc] fix: using-events graphql error (#20618)

## Description 

The GraphQL in [Query events with
GraphQL](https://docs.sui.io/guides/developer/sui-101/using-events#query-events-with-graphql)
has error

## Test plan 
1.
[crates/sui-graphql-rpc/examples/event_connection/event_connection.graphql](https://github.com/MystenLabs/sui/tree/main/crates/sui-graphql-rpc/examples/event_connection/event_connection.graphql)
and
[crates/sui-graphql-rpc/examples/event_connection/filter_by_sender.graphql](https://github.com/MystenLabs/sui/tree/main/crates/sui-graphql-rpc/examples/event_connection/filter_by_sender.graphql)

throw the error

```json
{
  "data": null,
  "errors": [
    {
      "message": "Unknown field \"type\" on type \"Event\".",
      "locations": [
        {
          "line": 18,
          "column": 7
        }
      ]
    },
    {
      "message": "Unknown field \"json\" on type \"Event\".",
      "locations": [
        {
          "line": 25,
          "column": 7
        }
      ]
    }
  ]
}
```

need to be modified to
```
contents {
  type {
    repr
  }
  json
}
```

2.
[crates/sui-graphql-rpc/examples/event_connection/filter_by_emitting_package_module_and_event_type.graphql](https://github.com/MystenLabs/sui/tree/main/crates/sui-graphql-rpc/examples/event_connection/filter_by_emitting_package_module_and_event_type.graphql)

throw the error

```json
{
  "data": null,
  "errors": [
    {
      "message": "Filtering by both emitting module and event type is not supported",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
      "path": [
        "events"
      ],
      "extensions": {
        "code": "BAD_USER_INPUT"
      }
    }
  ]
}
```

Read the [EventFilter.emittingModule
doc](https://docs.sui.io/references/sui-api/sui-graphql/reference/types/inputs/event-filter#eventfilteremittingmodulestring-),
it says `We currently do not support filtering by emitting module and
event type at the same time so if both are provided in one filter, the
query will error.`.

So I think the doc need to delete the example `[Filter events by
emitting package and type]`

---

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] Indexer: 
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] REST API:

crates/sui-graphql-rpc/examples/event_connection/event_connection.graphql

@@ -9,15 +9,17 @@
         name
         package { digest }
       }
-      type {
-        repr
-      }
       sender {
         address
       }
       timestamp
-      json
+      contents {
+        type {
+          repr
+        }
+        json
+      }
       bcs
     }
   }
-}
+}

crates/sui-graphql-rpc/examples/event_connection/filter_by_sender.graphql

@@ -13,14 +13,16 @@ query ByTxSender {
       sendingModule {
         name
       }
-      type {
-        repr
+			contents {
+        type {
+          repr
+        }
+        json
       }
       sender {
         address
       }
       timestamp
-      json
       bcs
     }
   }

docs/content/guides/developer/sui-101/using-events.mdx

@@ -311,13 +311,6 @@ Filter events by sender
 {@inject: crates/sui-graphql-rpc/examples/event_connection/filter_by_sender.graphql}
 </details>
 
-<details>
-<summary>
-Filter events by emitting package and type
-</summary>
-{@inject: crates/sui-graphql-rpc/examples/event_connection/filter_by_emitting_package_module_and_event_type.graphql}
-</details>
-
 The [TypeScript SDK](https://sdk.mystenlabs.com/typedoc/modules/_mysten_sui.graphql.html) provides functionality to interact with the Sui GraphQL service.
 
 ## Monitoring events