[move.sentinel] Use "std::move" in example for correctness (#6043)

Author: hewillk

source/iterators.tex

@@ -5259,7 +5259,8 @@
          @\libconcept{indirect_unary_predicate}@<I> Pred>
   requires @\libconcept{indirectly_movable}@<I, O>
 void move_if(I first, S last, O out, Pred pred) {
-  ranges::copy_if(move_iterator<I>{first}, move_sentinel<S>{last}, out, pred);
+  ranges::copy_if(move_iterator<I>{std::move(first)}, move_sentinel<S>{last},
+                  std::move(out), pred);
 }
 \end{codeblock}
 \end{example}