Disable tests for SI-7020

These are still impudently being non-deterministic.

I've reopened the ticket so we can take another swing at it.
A well targetted s/HashMap/LinkedHashMap/ will almost certainly
be the salve.

	fail - neg/t7020.scala  [output differs]% scalac t7020.scala
	t7020.scala:3: warning: match may not be exhaustive.
	It would fail on the following inputs: List((x: Int forSome x not in (1, 2, 4, 5, 6, 7))), List((x: Int forSome x not in (1, 2, 4, 5, 6, 7)), _), List(1, _), List(2, _), List(4, _), List(5, _), List(6, _), List(7, _), List(??, _), List(_, _)
	 List(5) match {
	     ^
	t7020.scala:10: warning: match may not be exhaustive.
	It would fail on the following inputs: List((x: Int forSome x not in (1, 2, 4, 5, 6, 7))), List((x: Int forSome x not in (1, 2, 4, 5, 6, 7)), _), List(1, _), List(2, _), List(4, _), List(5, _), List(6, _), List(7, _), List(??, _), List(_, _)
	 List(5) match {
	     ^

Author: retronym