JVM: remove support for disabling NoConstantValueAttributeForNonConstVals

This feature is enabled by default since 1.4, which is the earliest
language version supported by Kotlin at this moment.

compiler/testData/loadJava/compiledKotlin/prop/nonConstValWithConstantValueAttribute.kt

@@ -1,19 +0,0 @@
-// !LANGUAGE: -NoConstantValueAttributeForNonConstVals
-//ALLOW_AST_ACCESS
-
-package test
-val nonConstVal1 = 1
-
-class C {
-    val nonConstVal2 = 2
-
-    companion object {
-        val nonConstVal3 = 3
-    }
-}
-
-interface I {
-    companion object {
-        val nonConstVal4 = 4
-    }
-}