rm get-communicator test dependence on mpi module

not needed when compilering with "caf"

Author: Damian Rouson

src/tests/unit/teams/get-communicator.f90

@@ -84,7 +84,6 @@ pure function destination_team(image,numTeams) result(team)
 
   subroutine mpi_matches_caf(comm)
     use iso_c_binding, only : c_int
-    use mpi, only : MPI_COMM_SIZE, MPI_COMM_RANK
     integer(c_int), intent(in) :: comm
       !! MPI communicator
     integer(c_int) :: isize,ierror,irank