Minor, remove obsolete directives and suppressions from contracts test data

compiler/testData/codegen/boxInline/contracts/exactlyOnceCrossinline2.kt

@@ -1,4 +1,3 @@
-// !LANGUAGE: +AllowContractsForCustomFunctions +UseCallsInPlaceEffect +ReadDeserializedContracts
 // !USE_EXPERIMENTAL: kotlin.contracts.ExperimentalContracts
 // IGNORE_BACKEND: NATIVE
 // FILE: 1.kt
@@ -6,7 +5,6 @@ package test
 
 import kotlin.contracts.*
 
-@ExperimentalContracts
 class A {
     var res = "FAIL"
 
@@ -23,7 +21,6 @@ class A {
     }
 }
 
-@ExperimentalContracts
 inline fun baz(crossinline exactly_once: () -> Unit) {
     contract {
         callsInPlace(exactly_once, InvocationKind.EXACTLY_ONCE)