Update screenshots

> https://github.com/Kunzisoft/KeePassDX/tree/master/fastlane/metadata/android/en-US/images/phoneScreenshots

The F-Droid screenshots are too old. Lot of things has been changed in 2years, update them with our material design app screenshots. If necessary change featureGraphic as well.

If you've some time, change with half-B&W screenshots like [this app](https://github.com/MuntashirAkon/AppManager#screenshots) or [this website](https://github.com/lichess-org/lila#lichessorg)...

Note: The v`4.1.2` is already released so the metadata changes won't be picked up for F-Droid this time.

Review the existing files under fastlane/metadata/android/en-US/images/phoneScreenshots and compare them with the current material design app. Capture and replace the outdated F-Droid screenshots, and update featureGraphic if needed; use the linked AppManager and lichess examples as optional visual references. Done means the metadata contains current screenshots and any intended feature graphic update.

Written by the indexing model from the issue text.