Typo correction for d-i i18n and l10n Guide

[Tapio Lehtonen <tale@iki.fi>]

89c89
< <filename>po/*.po</filename>: program translations. The maintainers unfortunately does not keep a templates file in their repositories, so translators should pick up another PO file as a reference to create their own translation file.
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> <filename>po/*.po</filename>: program translations. The maintainers unfortunately do not keep a templates file in their repositories, so translators should pick up another PO file as a reference to create their own translation file.