proto: Remove superfluous else in handle

The body of the if statement always returns from the function, so the
`else if` can simply be another `if`.

quinn-proto/src/endpoint.rs

@@ -286,7 +286,9 @@ impl Endpoint {
                     None
                 }
             };
-        } else if first_decode.has_long_header() {
+        }
+
+        if first_decode.has_long_header() {
             debug!(
                 "ignoring non-initial packet for unknown connection {}",
                 dst_cid