Stop text polling when navigating away from the page

[juliusknorr]

• Go to another app
• If the loading takes longer, text sync endpoint is still being polled during the initial page load of the next page

[mejo-]

I'm pretty sure we fixed this somewhere along the road. I'll close this for now but please don't hesitate to comment/reopen if you think it's still a thing @juliusknorr @max-nextcloud