This disable a theia security feature of using a different hostname for
each webview. By defaut, for each webview, thiea generate an unique
hostname that when using vifib frontends would be something like
https://uuid.webview.softinstXXX.host.vifib.net but that's not usable in
our case because we cannot create frontends for a subdomain (also we
don't have certificates for such domain).

Configure THEIA_WEBVIEW_EXTERNAL_ENDPOINT to something less secure, but
working in our environment. This fixes embedded jupyter notebooks and
other web views.