Another blacklisted test

We have to do something about these from tasty tests. The way things are it's
downright torture for anyone who does significant compiler changes.

I sometimes spend more time fixing these tasty tests (all of them false negatives!)
than fixing the actual bug.

Author: odersky

compiler/test/dotc/pos-from-tasty.blacklist

@@ -21,7 +21,8 @@ i3050.scala
 i4006b.scala
 i4006c.scala
 
-# Not sure what's wring here
+# Not sure what's wrong here
 i4203.scala
 t6278-synth-def.scala
-t802.scala
+t802.scala
+i5997.scala