[expr.const]p14 example incorrect after P1937R2

[zygoloid]

After the application of P1937R2, this example from the end of [expr.const]p14 is no longer correct or useful:

[ Example:

struct N {
  constexpr N() {}
  N(N const&) = delete;
};
template<typename T> constexpr void bad_assert_copyable() { T t; T t2 = t; }
using ineffective = decltype(bad_assert_copyable<N>());
                        // bad_­assert_­copyable<N> is not needed for constant evaluation
                        // (and thus not instantiated)
template<typename T> consteval void assert_copyable() { T t; T t2 = t; }
using check = decltype(assert_copyable<N>());
                        // error: assert_­copyable<N> is instantiated (because it is needed for constant
                        // evaluation), but the attempt to copy t is ill-formed

— end example ]

The distinction it's trying to draw attention to was removed by P1937R2, so let's just remove the example rather than trying to fix it.