Remove unused ad-hoc test files

regression/invalid/Array1.scala

regression/invalid/Array2.scala

regression/invalid/Array3.scala

regression/invalid/Array4.scala

regression/invalid/Array5.scala

regression/invalid/Epsilon1.scala

regression/invalid/Epsilon2.scala

regression/invalid/Epsilon3.scala

regression/invalid/Epsilon4.scala

regression/invalid/Epsilon5.scala

regression/invalid/Epsilon6.scala

regression/invalid/IfExpr1.scala

regression/invalid/IfExpr2.scala

regression/invalid/MyTuple1.scala

regression/invalid/MyTuple2.scala

regression/invalid/MyTuple3.scala

regression/invalid/Unit1.scala

regression/valid/Array1.scala

regression/valid/Array10.scala

regression/valid/Array2.scala