Update main-de.json (#5905)

The word "Weitere" implied that there are already people in the meeting so I replaced it with "andere". 
I also made line 775 gender-neutral as "der Einzige" would technically only refer to males which isn't an unusual thing to do but some people might consider it discriminatory against women.

lang/main-de.json

         "title": "Sichere, mit umfassenden Funktionen ausgestattete und vollkommen kostenlose Videokonferenzen"
     },
     "lonelyMeetingExperience": {
-        "button": "Weitere einladen",
-        "youAreAlone": "Sie sind der Einzige in diesem Meeting"
+        "button": "Andere einladen",
+        "youAreAlone": "Nur Sie sind in diesem Meeting"
     }
 }