Clarify what will be downloaded

Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/html/translation-download.html

 {% load i18n %}
 
-<li><a href="{% url 'download_translation' project=object.subproject.project.slug subproject=object.subproject.slug lang=object.language.code %}" title="{% trans "Download for an offline translation." %}">{% trans "Download source file" %}</a></li>
+<li><a href="{% url 'download_translation' project=object.subproject.project.slug subproject=object.subproject.slug lang=object.language.code %}" title="{% trans "Download for an offline translation." %}">{% trans "Download original translation file" %}</a></li>
 <li><a href="{% url 'download_translation_format' project=object.subproject.project.slug subproject=object.subproject.slug lang=object.language.code format='xliff'%}" title="{% trans "Download for an offline translation." %}">{% trans "Download translation as XLIFF" %}</a></li>
 <li><a href="{% url 'download_translation_format' project=object.subproject.project.slug subproject=object.subproject.slug lang=object.language.code format='po'%}" title="{% trans "Download for an offline translation." %}">{% trans "Download translation as Gettext PO" %}</a></li>
 {% if object.supports_language_pack %}