Silence further deprecation warning

src/google/protobuf/arena_unittest.cc

@@ -809,6 +809,7 @@ TEST(ArenaTest, AddAllocatedWithReflection) {
 TEST(ArenaTest, RepeatedPtrFieldAddClearedTest) {
 #ifndef PROTOBUF_FUTURE_REMOVE_CLEARED_API
   {
+    PROTOBUF_IGNORE_DEPRECATION_START
     RepeatedPtrField<TestAllTypes> repeated_field;
     EXPECT_TRUE(repeated_field.empty());
     EXPECT_EQ(0, repeated_field.size());
@@ -817,6 +818,7 @@ TEST(ArenaTest, RepeatedPtrFieldAddClearedTest) {
     repeated_field.AddCleared(cleared);
     EXPECT_TRUE(repeated_field.empty());
     EXPECT_EQ(0, repeated_field.size());
+    PROTOBUF_IGNORE_DEPRECATION_STOP
   }
 #endif  // !PROTOBUF_FUTURE_REMOVE_CLEARED_API
   {