Update Rust crate axum to v0.7.8

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
axum	dependencies	patch	0.7.7 -> 0.7.8

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Release Notes

tokio-rs/axum (axum)

v0.7.8: axum - v0.7.8

Compare Source

• fixed: Skip SSE incompatible chars of serde_json::RawValue in Event::json_data (#​2992)
• added: Add method_not_allowed_fallback to set a fallback when a path matches but there is no handler for the given HTTP method (#​2903)
• added: Add MethodFilter::CONNECT, routing::connect[_service]
  and MethodRouter::connect[_service] (#​2961)
• added: Add NoContent as a self-described shortcut for StatusCode::NO_CONTENT (#​2978)

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