feat: Remove get-auth-chain command

It's not really useful to just know how long loading an auth chain took

src/admin/debug/mod.rs

@@ -16,12 +16,6 @@ pub enum DebugCommand {
 		message: Vec<String>,
 	},
 
-	/// Loads the auth_chain of a PDU, reporting how long it took.
-	GetAuthChain {
-		/// An event ID (the $ character followed by the base64 reference hash)
-		event_id: OwnedEventId,
-	},
-
 	/// Walks & displays the auth_chain of a PDU in a mermaid graph format.
 	///
 	/// This is useless to basically anyone but developers, and is also probably