Remove bytecode text test kt15806.kt

It's not correct to expect that the backend generates the `when` in this
test as tableswitch because there are only two branches. JVM IR has a
cutoff in the when optimization and generates `when`s with fewer than 3
branches as if-else chains, which is probably better. Note that there's
also a corresponding box test in when/enumOptimization/, so the backend
behavior is still tested.

compiler/testData/codegen/bytecodeText/whenEnumOptimization/kt15806.kt

@@ -1,29 +0,0 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36845 Generate enum-based TABLESWITCH/LOOKUPSWITCH on a value with smart cast to enum in JVM_IR
-
-private fun Any?.doTheThing(): String {
-    when (this) {
-        is String -> return this
-        is Level -> {
-            when (this) {
-                Level.O -> return Level.O.name
-                Level.K -> return Level.K.name
-            }
-        }
-
-        else -> return "fail"
-    }
-}
-
-
-enum class Level {
-    O,
-    K
-}
-
-
-fun box(): String {
-    return "O".doTheThing() + Level.K.doTheThing()
-}
-
-// 1 TABLESWITCH