[range.concat.iterator] Fix indentation (#6937)

Author: Andreas-Krug

source/ranges.tex

@@ -8792,7 +8792,7 @@
       requires (@\exposconcept{all-random-access}@<Const, Views...> &&
                 (@\libconcept{three_way_comparable}@<iterator_t<@\exposid{maybe-const}@<Const, Views>>> && ...));
     friend constexpr @\exposid{iterator}@ operator+(const @\exposid{iterator}@& it, difference_type n)
-        requires @\exposconcept{concat-is-random-access}@<Const, Views...>;
+      requires @\exposconcept{concat-is-random-access}@<Const, Views...>;
     friend constexpr @\exposid{iterator}@ operator+(difference_type n, const @\exposid{iterator}@& it)
       requires @\exposconcept{concat-is-random-access}@<Const, Views...>;
     friend constexpr @\exposid{iterator}@ operator-(const @\exposid{iterator}@& it, difference_type n)