[iterator.synopsis] Update projected in the synopsis of <iterator>

Author: frederick-vs-ja

source/iterators.tex

@@ -169,7 +169,7 @@
 
   // \ref{projected}, projected
   template<@\libconcept{indirectly_readable}@ I, @\libconcept{indirectly_regular_unary_invocable}@<I> Proj>
-    struct projected;                                                               // freestanding
+    using projected = @\seebelow@;                                                    // freestanding
 
   template<@\libconcept{indirectly_readable}@ I, @\libconcept{indirectly_regular_unary_invocable}@<I> Proj>
   using projected_value_t =                                                         // freestanding