Fix - App is Using Battery Notification
Swipe down on the notification shade, to bring up the “ app is using battery” notification
Long press on that notification (or slide it left if that doesn't work) and new setting cog will pop up with a toggle button right next to it.
Tap on the toggle, to disable it.
Save changes by taping on the 'Save' option at the bottom. And it should hide the persistent notification. Do note, this only hides the notification, the app is still running in the background. If it's not an active app like a music player or podcast, you need to 'Force close' it.
Alternatively, you can install Hide "Running in the background" Notification app from the Google Play Store. As long as you have this app installed, you won't see any persistent notification on your phone.
Updated: October 9, 2021