linux: add missing break to get rid of error message

Streaming recently got its own priority, but due to the missing
break, Low priority threads would fall through, causing the
call to fail since processes cannot increase their priority.

Therefore, the behaviour doesn't really change except for the
error going away.

WickedEngine/wiJobSystem.cpp

@@ -204,6 +204,7 @@ namespace wi::jobsystem
 						{
 							perror("setpriority");
 						}
+						break;
 					case Priority::Streaming:
 						if (setpriority(PRIO_PROCESS, 0, 2) != 0)
 						{