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

#KT-6402 Fixed

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

@@ -4,10 +4,10 @@
 fun foo(a: Int) {
     val b: Int = 1
 
-    unit(a)
+    __dummyTestFun__(a)
 }
 
-private fun unit(a: Int) {
+private fun __dummyTestFun__(a: Int) {
     var t = a
     while (t > 0) {
         if (t == 2) continue