git: openjdk/loom: fibers: Move incorrect assertion

[duke]

Changeset: a20642d3
Author:    Ron Pressler <ron.pressler at oracle.com>
Date:      2021-03-31 17:29:56 +0000
URL:       https://git.openjdk.java.net/loom/commit/a20642d3

Move incorrect assertion

! src/hotspot/share/runtime/continuation.cpp