calendar: Filter out newlines when unexpanded

Enabling line-wrapping of the unexpanded body is not enough to enforce
a single line when the text has embedded newlines, so replace these with
spaces (this is similar to setting ClutterText:single-line-mode, however
that would use a paragraph separator glyph instead).

js/ui/calendar.js

@@ -1044,7 +1044,7 @@ const Message = new Lang.Class({
 
     setBody: function(text) {
         this._bodyText = text;
-        this.bodyLabel.setMarkup(text, this._useBodyMarkup);
+        this.bodyLabel.setMarkup(text.replace(/\n/g, ' '), this._useBodyMarkup);
     },
 
     setUseBodyMarkup: function(enable) {