Bug 1652281 - Remove assertion about empty chunks pool that no longer always holds r=sfink

GCRuntime::decommitFreeArenasWithoutUnlocking can now get called in situations when we do have empty chunks, e.g. when handling OOM in GCRuntime::decommitFreeArenas. We can just remove this assertion.

Differential Revision: https://phabricator.services.mozilla.com/D83295

js/src/gc/GC.cpp

@@ -3276,7 +3276,6 @@ void GCRuntime::decommitFreeArenas(const bool& cancel, AutoLockGC& lock) {
 // Do all possible decommit immediately from the current thread without
 // releasing the GC lock or allocating any memory.
 void GCRuntime::decommitFreeArenasWithoutUnlocking(const AutoLockGC& lock) {
-  MOZ_ASSERT(emptyChunks(lock).count() == 0);
   for (ChunkPool::Iter chunk(availableChunks(lock)); !chunk.done();
        chunk.next()) {
     chunk->decommitFreeArenasWithoutUnlocking(lock);