fix: return error when trying to unregister unknown appservice id

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/utils/error.rs

@@ -76,6 +76,8 @@ pub enum Error {
 	RedactionError(OwnedServerName, ruma::canonical_json::RedactionError),
 	#[error("{0} in {1}")]
 	InconsistentRoomState(&'static str, ruma::OwnedRoomId),
+	#[error("{0}")]
+	AdminCommand(&'static str),
 }
 
 impl Error {