SI-8151 Prepare for removal of -Yself-in-annots

Upstream, Scala will remove the `selfsym` field from `AnnotatedType`.

This commit removes its uses in Scala IDE:

  1. In debug printing code
  2. In a commented-out pattern match
Merge pull request #627 from retronym/topic/annotated-no-self-sym

SI-8151 Prepare for removal of -Yself-in-annots