Remove heap warnings when using buffered finalisation

The allocation of pages for the finaliser buffer is done from within the
STW pause. This can cause the heap to grow if lots of objects are
enqueued for finalisation in a single GC and can cause spurious warnings
to be printed to stderr.

misc.c

@@ -2069,9 +2069,11 @@ GC_API void GC_CALL GC_enable(void)
     LOCK();
     GC_ASSERT(GC_dont_gc != 0); /* ensure no counter underflow */
     GC_dont_gc--;
+#ifndef BUFFERED_FINALIZATION
     if (!GC_dont_gc && GC_heapsize > GC_heapsize_on_gc_disable)
       WARN("Heap grown by %" WARN_PRIuPTR " KiB while GC was disabled\n",
            (GC_heapsize - GC_heapsize_on_gc_disable) >> 10);
+#endif
     UNLOCK();
 }