slapos_jio_ui_test: Fix typo in the test testSlapOSJSServer

According to this [code](https://lab.nexedi.com/nexedi/slapos.core/blob/master/master/bt5/slapos_jio/PathTemplateItem/web_page_module/rjs_gadget_erp5_page_slap_computer_view_js.js#L127) . I believe the test `testSlapOSJSServer` currently failed due to a typo. There may have other failing in this test, but at least we can fix this one first.

/reviewed-on !165