It is not hosted by us it hosted by you. 192.168.0.34 would be the IP address you typed in the browser that is your computer or whatever you have the Plex Media Server installed on.
https://app.plex.tv is hosted by Plex.
the reason it is there is because unsuspecting users get duped by unscrupulous people to connect to some other server hosted by that unscrupulous person then they may attempt to steal the users credential for example.
There should be a continue with the account that it shows or sign in button. complete signing in. If you do not have your browser set to delete cookies/site data every time you close it then it should not ask again on that browser
