group_from_session_pset - remove confusing error message

The implementation of MPI_Group_from_session_pset was emitting
a confusing error message when querying the PMIx server for
members of a process group.  The routine was using a
method for creating an error message that was intended to be
using during mpi initialization.

Remove that statement and let an error code be returned.

Related to #13497

Signed-off-by: Howard Pritchard <howardp@lanl.gov>

Author: hppritcha

ompi/instance/instance.c

@@ -1313,7 +1313,6 @@ static int ompi_instance_group_pmix_pset (ompi_instance_t *instance, const char
             ret = opal_pmix_convert_status(rc);
             break;
         }
-        ompi_instance_print_error ("PMIx_Query_info() failed", ret);
         goto fn_w_query;
     }
 
@@ -1334,7 +1333,6 @@ static int ompi_instance_group_pmix_pset (ompi_instance_t *instance, const char
 		if (OPAL_SUCCESS == rc) {
                     group->grp_proc_pointers[i] = ompi_proc_find_and_add(&pname,&isnew);
                 } else {
-                    ompi_instance_print_error ("OPAL_PMIX_CONVERT_PROCT failed %d", ret);
                     ompi_group_free(&group);
                     goto fn_w_info;
                 }