Use ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS in stable_block_list.h

Replaces the standard [[no_unique_address]] attribute with the Abseil macro ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS, which doesn't work in win environment.

PiperOrigin-RevId: 967775335

quiche/common/stable_block_list.h

diff --git a/quiche/common/stable_block_list.h b/quiche/common/stable_block_list.h
index 6c9ef67..18c535a 100644
--- a/quiche/common/stable_block_list.h
+++ b/quiche/common/stable_block_list.h
@@ -558,7 +558,7 @@
     }
   }
 
-  [[no_unique_address]] Allocator allocator_;
+  ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS Allocator allocator_;
   absl_nullable std::unique_ptr<ControlBlock> control_block_;
 };