[expr.const] Remove example that was made incorrect by P1937R2.

Fixes #3792.

Author: zygoloid

source/expressions.tex

@@ -7366,21 +7366,4 @@
 is of non-volatile const-qualified integral type or of reference type.
 \end{itemize}
 
-\begin{example}
-\begin{codeblock}
-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>());
-                        // \tcode{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: \tcode{assert_copyable<N>} is instantiated (because it is needed for constant
-                        // evaluation), but the attempt to copy \tcode{t} is ill-formed
-\end{codeblock}
-\end{example}
-
 \indextext{expression|)}