fix typo from r25958. Thanks to Nikerabbit

diff --git a/maintenance/language/messages.inc b/maintenance/language/messages.inc
index aa9a2a4..898812c 100644 (file)
--- a/maintenance/language/messages.inc
+++ b/maintenance/language/messages.inc
@@ -1290,7 +1290,7 @@ $wgMessageStructure = array(
                'uctop',
                'month',
                'year',
-               'year_month',
+               'year-month',
        ),
        'sp-contributions' => array(
                'sp-contributions-newest',