Extract Function: Do not suggest "unit" as function name

#KT-6402 Fixed

idea/testData/refactoring/extractFunction/controlFlow/default/defaultCFWithExtraVars.kt.after

@@ -8,13 +8,13 @@ fun foo(a: Int) {
     val b: Int = 1
 
     val c: Int
-    unit(a, b)
+    __dummyTestFun__(a, b)
 
     c = 1
     println(c)
 }
 
-private fun unit(a: Int, b: Int) {
+private fun __dummyTestFun__(a: Int, b: Int) {
     if (a > 0) {
         println(a)
     }