Remove backend tests on old inference

Also remove any mentions of NewInference, and rename some tests.

compiler/testData/codegen/box/inference/builderInference.kt

@@ -1,6 +1,5 @@
 // TARGET_BACKEND: JVM
 // WITH_RUNTIME
-// !LANGUAGE: +NewInference
 // ISSUE: KT-33545
 
 import kotlin.experimental.ExperimentalTypeInference
@@ -29,4 +28,4 @@ fun <Value> Flow<Value>.asLiveData() = liveData {
 //    collect { emit(it) }
 }
 
-fun box(): String = "OK"
+fun box(): String = "OK"