This solution from Sk4nk77 fixed it for me.
“Hey guys, I think I've found the solution to this annoying issue. I have had the download stuck on my phone for maybe a week, a pop-up window prompting me to download the language update literally every time I've unlocked my phone . Aarghhh, nothing seems to work. Even the OS update didn't get rid of the issue. However, I've recently tried this, and it seems to have fixed it. 🤞Go to "voice access settings" and click on "Help and feedback" then from the sandwich menu (top right). Select "View in Google Play store." Open it with the Play Store and then uninstall it. Confirm that you want to remove all the updates. After this, both buttons have disappeared, but the app still remained installed. I've then gone back to voice access settings and got prompted again to download the language update. However, this time, when I pressed Download, another window appeared, asking me to confirm the download of ~65MB. So I've confirmed that, and it seems to have worked.“
Good luck.
