[Backport] 8234684: JFR crashes when rotating the JFR output during assertion failure

Summary:

Test Plan: jdk/jfr

Reviewed-by: yuleil

Issue: https://github.com/alibaba/dragonwell8/issues/112

src/share/vm/jfr/recorder/checkpoint/jfrCheckpointManager.cpp

@@ -494,7 +494,6 @@ bool JfrCheckpointManager::is_type_set_required() {
 }
 
 size_t JfrCheckpointManager::flush_type_set() {
-  assert(!SafepointSynchronize::is_at_safepoint(), "invariant");
   size_t elements = 0;
   {
     JfrCheckpointWriter writer(Thread::current());