That's definitely not true, most people at my sixth form did 3 AS levels and have had no trouble getting university offers, even from Russel Group universities. The most prestigious universities will be unlikely to accept you though, and the same goes for certain courses such as medicine. But to be honest with languages A-level you either really go for it or you do badly, so if it's the subject you're giving least priority and attention to then it may well make sense to drop it, especially if you would drop it at the end of year 12 anyway.