BotManagerInterface.as: change required for Sven Co-op 5.26

[Outerbeast]

BotManagerInterface.as Line 806 needs to be changed to this: HookReturnCode MapChange(const string& in sLevel)

From SC 5.26 Changelog:

• Hook "MapChange" now receives a string to reveal which map the server is about to change to, or empty if the server is shutting down. ALL scripts listening for this "MapChange" event will need an update. Just add a parameter for a string to receive the new map.

Cheers