deposit: string fix in templates

 (addresses #1915)

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
`<button class="btn btn-default form-save" data-toggle="tooltip" title="{{_('Press "Save" to save your upload for editing later, as many times you like.')}}" ><i class="fa fa-file-o"></i> {{ _('Save') }}</button>`