PDF Upload button now refers to "PDF" rather than "asset"

cms/templates/js/edit-chapter.underscore

@@ -9,6 +9,6 @@
   <label for="chapter<%= order %>-asset-path"><%= gettext("Chapter Asset") %></label>
   <input id="chapter<%= order %>-asset-path" name="chapter<%= order %>-asset-path" class="chapter-asset-path" placeholder="<%= _.str.sprintf(gettext("path/to/introductionToCookieBaking-CH%d.pdf"), order) %>" value="<%= asset_path %>" type="text">
   <span class="tip tip-stacked"><%= gettext("upload a PDF file or provide the path to a Studio asset file") %></span>
-<button class="action action-upload"><%= gettext("Upload Asset") %></button>
+<button class="action action-upload"><%= gettext("Upload PDF") %></button>
 </div>
 <a href="" class="action action-close"><i class="icon-remove-sign"></i> <span class="sr"><%= gettext("delete chapter") %></span></a>