t5318-commit-graph.sh breaks travis gettext poison job

[Duy Nguyen <pclouds@xxxxxxxxx>]

In case you're not checking travis, [1] reports

Test Summary Report
-------------------
t5318-commit-graph.sh                            (Wstat: 256 Tests: 62
Failed: 2)
  Failed tests:  61-62
  Non-zero exit status: 1

This usually means you're grepping an i18n string

[1] https://travis-ci.org/git/git/jobs/386532326

-- 
Duy