[range.concat.iterator] Remove spurious newline (#8982)

Author: hewillk

source/ranges.tex

@@ -9070,7 +9070,6 @@
               @\exposconcept{concatable}@<Views...>
   template<bool Const>
   class concat_view<Views...>::@\exposid{iterator}@ {
-
   public:
     using iterator_category = @\seebelow@;                                // not always present
     using iterator_concept = @\seebelow@;