[memory.syn] Delete unintended synopsis entry for "destroy_at".

This seems to have been a mistake in applying P3179R9.

Author: tkoeppe

source/memory.tex

@@ -502,9 +502,6 @@
       requires @\libconcept{destructible}@<iter_value_t<I>>
         constexpr I destroy_n(I first, iter_difference_t<I> n) noexcept;            // freestanding
 
-    template<@\exposconcept{execution-policy}@ Ep, @\libconcept{destructible}@ T>
-      void destroy_at(Ep&& exec, T* location) noexcept;                     // freestanding-deleted
-
     template<@\exposconcept{execution-policy}@ Ep, @\exposconcept{nothrow-random-access-iterator}@ I, @\exposconcept{nothrow-sentinel-for}@<I> S>
       requires @\libconcept{destructible}@<iter_value_t<I>>
         I destroy(Ep&& exec, I first, S last) noexcept;                     // freestanding-deleted,