[alg.searc] Fixed transcription error in template head

Author: tkoeppe

source/algorithms.tex

@@ -5989,7 +5989,7 @@
     ranges::search_n(Ep&& exec, I first, S last, iter_difference_t<I> count,
                      const T& value, Pred pred = {}, Proj proj = {});
 template<@\exposconcept{execution-policy}@ Ep, @\exposconcept{sized-random-access-range}@ R, class Pred = ranges::equal_to,
-         class Proj = identity, class T = projected_value_t<I, Proj>>
+         class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>>
   requires @\libconcept{indirectly_comparable}@<iterator_t<R>, const T*, Pred, Proj>
   borrowed_subrange_t<R>
     ranges::search_n(Ep&& exec, R&& r, range_difference_t<R> count,