Lock axum to 0.7.4

Version 0.7.5 triggers a warning in
our version of rust nightly in CI,
but we can't update it to a recent
version because it triggers a warning
caused by displaydoc

Signed-off-by: Kévin Commaille <[email protected]>

Author: zecakeh

Cargo.lock

@@ -70,7 +70,7 @@ as_variant = { workspace = true }
 async-channel = "2.1.0"
 async-stream = { workspace = true }
 async-trait = { workspace = true }
-axum = { version = "0.7.5", optional = true }
+axum = { version = "0.7.4", optional = true }
 bytes = "1.1.0"
 bytesize = "1.1"
 cfg-vis = "0.3.0"