calendar url inpits: replace disable by readonly

tracim/tracim/templates/user_workspace_forms.mak

             <div class="form-group">
                 <label for="calendar">${_('Personal calendar')}</label>
                 <span class="info readonly">${_('This calendar URL will work with CalDav compatibles clients')}</span>
-                <input id="calendar" type="text" class="form-control"  disabled="disabled" value="${user.calendar_url}" />
+                <input id="calendar" type="text" class="form-control" readonly value="${user.calendar_url}" />
             </div>
         </div>
         <div class="modal-footer">

tracim/tracim/templates/workspace/edit.mak

         </script>
         <div class="form-group calendar-url" style="display: ${'none' if not result.workspace.calendar_enabled else 'block'};">
             <label for="workspace-name1">${_('Calendar Url')}</label>
-            <input id="workspaceCalendarUrl" type="text" class="form-control"  disabled="disabled" value="${result.workspace.calendar_url}" />
+            <input id="workspaceCalendarUrl" type="text" class="form-control" readonly value="${result.workspace.calendar_url}" />
             <p>
                 ${_('This url is the one to configure in your calendar software: Outlook, Thunderbird, etc.')}
             </p>