Fix build failure caused by wrong charset in it.po

Author: haginrich

po/it.po

@@ -14,7 +14,7 @@ msgstr ""
 "Language-Team: LANGUAGE <[email protected]>\n"
 "Language: \n"
 "MIME-Version: 1.0\n"
-"Content-Type: text/plain; charset=CHARSET\n"
+"Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"
 
 #: data/gtk/help-overlay.blp:11