Remove backend tests on old inference

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

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

@@ -1,4 +1,3 @@
-// !LANGUAGE: +NewInference
 // WITH_RUNTIME
 
 inline fun <T> foo(f: () -> T): String {
@@ -27,4 +26,4 @@ fun test(b: Boolean): String {
 
 fun box(): String {
     return test(true)
-}
+}