reverted change wrt. Erasable concept

src/json.hpp.re2c

@@ -143,9 +143,6 @@ default)
  - [ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer);
    JSON values can be used like STL containers and provide reverse iterator
    access.
-- Container Elements
- - [Eraseable](http://en.cppreference.com/w/cpp/concept/Erasable):
-   JSON values can be destroyed by a given allocator.
 
 @internal
 @note ObjectType trick from http://stackoverflow.com/a/9860911

test/unit.cpp

@@ -10767,24 +10767,6 @@ TEST_CASE("concepts")
 
         // the expression "X()" has the post-condition "X().empty()"
         CHECK(json().empty());
-
-
-        // from http://en.cppreference.com/w/cpp/concept/Container:
-        // T must be Eraseable
-        {
-            // prepare
-            auto m = json::get_allocator();
-            json* p = m.allocate(1);
-            m.construct(p, "foo");
-
-            // required
-            std::allocator_traits<json::allocator_type>::destroy(m, p);
-
-            CHECK(*p == "foo");
-
-            // cleanup
-            m.deallocate(p, 1);
-        }
     }
 
     SECTION("class json")