Update Mercurygram (`it.belloworld.mercurygram`)

Another update of Mercurygram has not been picked by autoupdate. Please update from 10.6.4.0 to 10.8.1.0

Thank you!

https://f-droid.org/en/packages/de.mm20.launcher2.release

https://gitlab.com/fdroid/fdroiddata/-/blob/master/metadata/it.belloworld.mercurygram.yml

https://github.com/drizzt/Mercurygram/releases/tag/10.8.1.0