[gnome-weather] Add translator comment to ambiguous string

[Giovanni Campagna <gcampagna src gnome org>]

commit b088d2c57c2b340d92d60b92ed559f1f62d39a03
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Mon Jun 23 22:17:21 2014 +0200

    Add translator comment to ambiguous string

 src/app/forecast.js |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/app/forecast.js b/src/app/forecast.js
index a13c7c0..baec9a3 100644
--- a/src/app/forecast.js
+++ b/src/app/forecast.js
@@ -353,6 +353,8 @@ const TodaySidebar = new Lang.Class({
         else
             this._headline.label = '<b>' + _("Forecast for Today") + '</b>';
 
+        // Translators: this is the date format for the sidebar date
+        // It's a long date (explicit day name), relative to this week
         this._subline.label = date.format(_("%B %d"));
     },