Minor: use ".touch" extension instead of ".new" in incremental compilation tests when it possible

jps-plugin/testData/incremental/pureKotlin/dependencyClassReferenced/a.kt.new

@@ -1,6 +0,0 @@
-package test
-
-fun a(ref: kotlin.test.Asserter) {
-    b(ref)
-    println(":)")
-}