specified the entity to be used in the example

Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Author: degawa

example/sorting/example_sort_bitsetl.f90

@@ -1,7 +1,7 @@
 program example_sort_bitsetl
   use stdlib_kinds, only: int32
   use stdlib_sorting, only: sort
-  use stdlib_bitsets
+  use stdlib_bitsets, only: bitset_large
   implicit none
   type(bitset_large), allocatable :: array(:)