fix(data_partition): remove unused variable

Author: Damian Rouson

tests/data_partition_test.f90

@@ -20,8 +20,6 @@ module data_partition_test
   function test_data_partition() result(tests)
     type(test_item_t) tests
 
-    integer iteration
-
     call partition%define_partitions( cardinality=num_particles)
 
     associate( me=>this_image() )