Remove unused ad-hoc test files

regression/valid/MyTuple1.scala

regression/valid/MyTuple2.scala

regression/valid/MyTuple3.scala

regression/valid/MyTuple4.scala

regression/valid/MyTuple5.scala

regression/valid/MyTuple6.scala

regression/valid/Nested1.scala

regression/valid/Nested10.scala

regression/valid/Nested11.scala

regression/valid/Nested12.scala

regression/valid/Nested13.scala

regression/valid/Nested14.scala

regression/valid/Nested2.scala

regression/valid/Nested3.scala

regression/valid/Nested4.scala

regression/valid/Nested5.scala

regression/valid/Nested6.scala

regression/valid/Nested7.scala

regression/valid/Nested8.scala

regression/valid/Nested9.scala