LU-18381 doc: Fix example in lctl-nodemap-modify.8

LU-18381 doc: Fix example in lctl-nodemap-modify.8

Use valid string in example instead of string that "currently works"

Test-Parameters: trivial
Fixes: 8a770616a5ad ("LU-14797 sec: add projid to nodemap")
Signed-off-by: Nathaniel Clark <nclark@whamcloud.com>
Change-Id: Ia3f55510ad398acb3729acfad174ade9e060a2ae
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56735
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Maximilian Dilger <mdilger@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>