fix(deps): update rust crate axum to 0.6.20

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
axum	dependencies	patch	0.6.19 -> 0.6.20

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Release Notes

tokio-rs/axum (axum)

### [`v0.6.20`](https://togithub.com/tokio-rs/axum/releases/tag/axum-v0.6.20): axum - v0.6.20 [Compare Source](https://togithub.com/tokio-rs/axum/compare/axum-v0.6.19...axum-v0.6.20) - **added:** `WebSocketUpgrade::write_buffer_size` and `WebSocketUpgrade::max_write_buffer_size` - **changed:** Deprecate `WebSocketUpgrade::max_send_queue` - **change:** Update tokio-tungstenite to 0.20 - **added:** Implement `Handler` for `T: IntoResponse` ([#​2140]) [#​2140]: https://togithub.com/tokio-rs/axum/pull/2140

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