Duplicate keys in en.json5 and de.json5

[saschaszott]

Describe the bug

There are several (> 50) keys that occur twice in en.json5 and de.json5, e.g.

• menu.section.icon.notifications
• form.number-picker.decrement
• form.number-picker.increment
• ...

For some duplicate keys, even the translations differ from each other, e.g.

"menu.section.icon.notifications": "Notifications menu section",
"menu.section.icon.notifications": "Notifictions menu section",