fix(stackable-webhook): enable axum http2 feature (#765)

Author: NickLarsenNZ

crates/stackable-webhook/Cargo.toml

@@ -10,7 +10,7 @@ repository.workspace = true
 stackable-certs = { path = "../stackable-certs", features = ["rustls"] }
 stackable-operator = { path = "../stackable-operator" }
 
-axum.workspace = true
+axum = { workspace = true, features = ["http2"] }
 futures-util.workspace = true
 hyper-util.workspace = true
 hyper.workspace = true