help: mark common_guides[] as translatable

Signed-off-by: Simon Ruderich <simon@ruderich.org>
Acked-by: Philip Oakley <philipoakley@iee.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'po/help-guides'

Finishing touches.

* po/help-guides:
  help: mark common_guides[] as translatable