Remove backend tests on old inference

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

compiler/testData/ir/irText/expressions/variableAsFunctionCallWithGenerics.kt

@@ -1,5 +1,3 @@
-// !LANGUAGE: +NewInference
-
 val <T : CharSequence> T.gk: () -> T
     get() = { -> this }
 
@@ -8,4 +6,4 @@ fun testGeneric1(x: String) = x.gk()
 val <T> T.kt26531Val: () -> T
     get() = fun () = this
 
-fun kt26531() = 7.kt26531Val()
+fun kt26531() = 7.kt26531Val()