[BUGFIX] do not add separator if interwiki links are on one line

added missing check for
site.language() in site.family.interwiki_on_one_line
follow-up for f706e8b89885ad8510fe17f8c87bed2c7f6e0db0

Change-Id: Idd5b80a1c7046dc4a299b948246e40a3eb682b72
Merge "[BUGFIX] do not add separator if interwiki links are on one line"