added info about smart casts to diagnostic tests

compiler/testData/diagnostics/tests/smartCasts/inference/kt2746.kt

@@ -5,7 +5,7 @@ class C<T>(t :T)
 
 fun test1(a: Any) {
     if (a is String) {
-        val <!UNUSED_VARIABLE!>c<!>: C<String> = C(a)
+        val <!UNUSED_VARIABLE!>c<!>: C<String> = C(<!DEBUG_INFO_AUTOCAST!>a<!>)
     }
 }
 
@@ -14,6 +14,6 @@ fun f<T>(t :T): C<T> = C(t)
 
 fun test2(a: Any) {
     if (a is String) {
-        val <!UNUSED_VARIABLE!>c1<!>: C<String> = f(a)
+        val <!UNUSED_VARIABLE!>c1<!>: C<String> = f(<!DEBUG_INFO_AUTOCAST!>a<!>)
     }
 }