make setting nullable

Author: sanderegg

services/web/server/src/simcore_service_webserver/collaboration/settings.py

@@ -12,7 +12,7 @@
 
 class RealTimeCollaborationSettings(BaseCustomSettings):
     RTC_MAX_NUMBER_OF_USERS: Annotated[
-        PositiveInt,
+        PositiveInt | None,
         Field(
             description="Maximum number of users allowed in a real-time collaboration session",
         ),