Reduce unnecessary combined_limit writes

src/coreclr/nativeaot/Runtime/gcenv.ee.cpp

@@ -143,7 +143,7 @@ void GCToEEInterface::GcEnumAllocContexts(enum_alloc_context_func* fn, void* par
         // combined_limit up-to-date. Note that the GC has multiple threads running this enumeration concurrently
         // with no synchronization. If you need to change this code think carefully about how that concurrency
         // may affect the results.
-        if (ac->alloc_limit == 0)
+        if (ac->alloc_limit == 0 && palloc_context->combined_limit != 0)
         {
             palloc_context->combined_limit = 0;
         }