chore(deps): update async-graphql to v6 (major) (#97)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [async-graphql](https://togithub.com/async-graphql/async-graphql) |
dependencies | major | `5.0.10` -> `6.0.4` |
| [async-graphql-axum](https://togithub.com/async-graphql/async-graphql)
| dependencies | major | `5.0.10` -> `6.0.4` |

---

### Release Notes

<details>
<summary>async-graphql/async-graphql (async-graphql)</summary>

###
[`v6.0.4`](https://togithub.com/async-graphql/async-graphql/blob/HEAD/CHANGELOG.md#604-2023-08-18)

- Parse "repeatable" in directive definitions.
[#&#8203;1336](https://togithub.com/async-graphql/async-graphql/pull/1336)
- add support `multipart/mixed` request.
[#&#8203;1348](https://togithub.com/async-graphql/async-graphql/issues/1348)
-   async-graphql-actix-web: add `GraphQL` handler.
-   async-graphql-axum: add `GraphQL` service.

###
[`v6.0.3`](https://togithub.com/async-graphql/async-graphql/blob/HEAD/CHANGELOG.md#603-2023-08-15)

- dynamic: fix the error that some methods of `XXXAccessor` return
reference lifetimes that are smaller than expected.
- dynamic: no longer throws an error if the Query object does not
contain any fields but the schema contains entities.
- chore: make accessors public and reexport indexmap
[#&#8203;1329](https://togithub.com/async-graphql/async-graphql/pull/1329)
- feat: added `OutputType` implementation for `std::sync::Weak`
[#&#8203;1334](https://togithub.com/async-graphql/async-graphql/pull/1334)

###
[`v6.0.1`](https://togithub.com/async-graphql/async-graphql/blob/HEAD/CHANGELOG.md#601-2023-08-02)

-   dynamic: remove `TypeRefInnner`
-   update MSRV to `1.67.0`

###
[`v6.0.0`](https://togithub.com/async-graphql/async-graphql/blob/HEAD/CHANGELOG.md#600-2023-07-29)

-   Bump `syn` from `1.0` to `2.0`
-   Bump `darling` from `0.14` to `0.20`
-   Bump `indexmap` from `1.6.2` to `2`
- Attributes `guard`, `process_with`, `complexity` support expression or
string as value
[#&#8203;1295](https://togithub.com/async-graphql/async-graphql/issues/1295)
- Schema (type) level directive support with optional support of
federation composeDirective
[#&#8203;1308](https://togithub.com/async-graphql/async-graphql/pull/1308)
- Add support for generic structs derriving InputObject and SimpleObject
[#&#8203;1313](https://togithub.com/async-graphql/async-graphql/pull/1313)
- chore: trim up some unnecessary code
[#&#8203;1324](https://togithub.com/async-graphql/async-graphql/pull/1324)
- Adds `Dataloader::get_cached_values` method to the dataloader cache so
that callers can access the contents of the cache without knowing the
keys.
[#&#8203;1326](https://togithub.com/async-graphql/async-graphql/pull/1326)

#### Breaking Changes

- Since `syn 2.0` no longer supports keywords as meta path, rename the
parameter used to specify interface field types from `type` to `ty`.


[dtolnay/syn#1458

[TedDriggs/darling#238

```rust

#[derive(Interface)]
#[graphql(field(name = "id", ty = "&i32"))] // rename from type to ty
enum Node {
    MyObj(MyObj),
}
```

- Change the parameter `location` of the macro `Directive` to
*PascalCase*

```rust
// #[Directive(location = "field")]

#[Directive(location = "Field")]
pub fn lowercase() -> impl CustomDirective {
    LowercaseDirective
}
```

</details>

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Cargo.toml

@@ -8,8 +8,8 @@ publish = false
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-async-graphql = { version = "5.0.10", default-features = false, features = ["tracing"] }
-async-graphql-axum = { version = "5.0.10", default-features = false }
+async-graphql = { version = "6.0.4", default-features = false, features = ["tracing"] }
+async-graphql-axum = { version = "6.0.4", default-features = false }
 async-trait = "0.1.73"
 axum = { version = "0.6.20", default-features = false, features = ["headers"] }
 headers = "0.3.8"