Add deprecated.scala to the blacklist to avoid cycles

Author: smarter

compiler/test/dotc/scala-collections.blacklist

@@ -1 +1,3 @@
-## The blacklist is currently empty
+## Compiling deprecated.scala together with other files sometimes leads to cycles.
+## e.g. try dotc scala2-library/src/library/scala/deprecated.scala scala2-library/src/library/scala/reflect/package.scala
+scala/deprecated.scala