G1: Improve assert in HeapRegion::reset_not_compacted_after_full_gc

the patch looks like below:

diff --git a/src/hotspot/share/gc/g1/heapRegion.inline.hpp b/src/hotspot/share/gc/g1/heapRegion.inline.hpp
index 19d610d927d..753771eabcb 100644
--- a/src/hotspot/share/gc/g1/heapRegion.inline.hpp
+++ b/src/hotspot/share/gc/g1/heapRegion.inline.hpp
@@ -199,7 +199,7 @@ inline void HeapRegion::reset_compacted_after_full_gc() {
 }

 inline void HeapRegion::reset_not_compacted_after_full_gc() {
- assert(!is_free(), "should not have compacted free region");
+ assert(!is_free(), "should have compacted free region");

   assert(compaction_top() == bottom(),
          "region %u compaction_top " PTR_FORMAT " must not be different from bottom " PTR_FORMAT,