Some headers get line breaks and don't follow the right format

The year is added to the translators credit line and at some point the line breaks in two and don't follow the right format:

    Jorge González <jorgegonz@svn.gnome.org>, 2009, 2010, 2011, 2012, 2013, 2014, 2015,
    ,2016, 2017, 2018.

Bugzilla reports:

• https://bugzilla.gnome.org/show_bug.cgi?id=673655
• https://bugzilla.gnome.org/show_bug.cgi?id=771765